Skip to main content

Full text of "Goethe's theory of colours"

This is a digital copy of a book that was preserved for generations on library shelves before it was carefully scanned by Google as part of a project 
to make the world's books discoverable online. 

It has survived long enough for the copyright to expire and the book to enter the public domain. A public domain book is one that was never subject 
to copyright or whose legal copyright term has expired. Whether a book is in the public domain may vary country to country. Public domain books 
are our gateways to the past, representing a wealth of history, culture and knowledge that's often difficult to discover. 

Marks, notations and other marginalia present in the original volume will appear in this file - a reminder of this book's long journey from the 
publisher to a library and finally to you. 

Usage guidelines 

Google is proud to partner with libraries to digitize public domain materials and make them widely accessible. Public domain books belong to the 
public and we are merely their custodians. Nevertheless, this work is expensive, so in order to keep providing this resource, we have taken steps to 
prevent abuse by commercial parties, including placing technical restrictions on automated querying. 

We also ask that you: 

+ Make non-commercial use of the files We designed Google Book Search for use by individuals, and we request that you use these files for 
personal, non-commercial purposes. 

+ Refrain from automated querying Do not send automated queries of any sort to Google's system: If you are conducting research on machine 
translation, optical character recognition or other areas where access to a large amount of text is helpful, please contact us. We encourage the 
use of public domain materials for these purposes and may be able to help. 

+ Maintain attribution The Google "watermark" you see on each file is essential for informing people about this project and helping them find 
additional materials through Google Book Search. Please do not remove it. 

+ Keep it legal Whatever your use, remember that you are responsible for ensuring that what you are doing is legal. Do not assume that just 
because we believe a book is in the public domain for users in the United States, that the work is also in the public domain for users in other 
countries. Whether a book is still in copyright varies from country to country, and we can't offer guidance on whether any specific use of 
any specific book is allowed. Please do not assume that a book's appearance in Google Book Search means it can be used in any manner 
anywhere in the world. Copyright infringement liability can be quite severe. 

About Google Book Search 

Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers 
discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web 

at http : //books . google . com/| 



Digitized by 



Google 



r-lfclUr J, 112 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 



THEORY OF COLOURS. 



Digitized by 



Google 



Digitized by 



Google 



GOETHE'S 



THEORY OF COLOURS; 



TRANSLATED FROM THE GERMAN: 



WITH NOTES BY 



CHARLES LOCK EASTLAEE, KA., F.B.S. 



** Cieero ▼mrieUtam pcoprM in eolorlbut naiol. hino in ali«niiiD mifrars ezittinmvii. 
CertA non alibi natom eopiodiu mut niviora iMctriA opet bou oommendmTit. Motalla. 
gamma*, mannorap floras, astra, omnia denlqiM qnm progenuit suit etiam coloribos dia* 
tinxii; at Tenia (Ubeatar ai qoia in iam nnnMTOsi nnun aylTi ealigaTerit.** 

Csuo CAMAomri. 



LONDON: 
JOHN MURRAY, ALBEMARLE STREET. 

1840. 



Digitized by 



Google 



LONDON: 

l*rlnUd by VVii.i.iam CtowRn and Soma, 

SfamfDrd Htrert. 







Digitized by 



Google 



TO 

JEREMIAH HABMAN, Esq. 

Dear Sir, 

I dedicate to you the following translation as a 
testimony of my sincere gratitude and respect ; in doing so» I 
but follow the example of Fortius, an Italian writer, who in* 
scribed his translation of Aristotle's Treatise on Colours to one of 
the Medici. 

I have the honour to be, 
Dear Sir, 
Your most obliged and obedient Servant, 

C. L. EASTLAKE. 



Digitized by 



Google 



Digitized by 



Google 



THE 



TRANSLATOR'S PREFACE. 



English writers who have spoken of Goethe's 
** Doctrine of Colours,"* have generally con- 
fined their remarks to those parts of the work 
in which he has undertaken to account for the 
colours of the prismatic spectrum, and of re- 
fraction altogether, on principles different from 
the received theory of Newton. The less ques- 
tionable merits of the treatise consisting of a 
well' arranged mass of observations and experi- 
ments, many of which are important and inter- 
esting, have thus been in a great measure over- 
looked. The translator, aware of the opposition 
which the theoretical views alluded to have met 
with, intended at first to make a selection of 

* '* Farbeulehre**-^iii the present translatioii generally rendered 
•* Theorv of Colours." 



Digitized by 



Google 



Vlll TRANSLATOR'S PREFACE. 

such of the experiments as seem more directly 
applicable to the theory and practice of paint- 
ing. Finding, however, that the alterations this 
would have involved would have been incom- 
patible with a clear and connected view of the 
author's statements, he preferred giving the 
theory itself entire, reflecting, at the same time, 
that some scientific readers may be curious to 
hear the author speak for himself even on the 
points at issue. 

In reviewing the history and progress of his 
opinions and researches, Goethe tells us that he 
first submitted his views to the public in two 
short essays entitled '* Contributions to Optics." 
Among the circumstances which he supposes 
were unfavourable to him on that occasion, he 
mentions the choice of his title, observing that 
by a reference to optics he must have appeared 
to make pretensions to a knowledge of mathe- 
matics, a science with which he admits he was 
very imperfectly acquainted. * Another cause to 
which he attributes the severe treatment he ex- 
perienced, was his having ventured so openly to 
question the truth of the established theory : 
but this last provocation could not be owing to 
mere inadvertence on his part ; indeed the larger 
work, in which he alludes to these circum- 



Digitized by 



Google 



TRANSLATOR'S PREFACE. IX 

Stances, is still more remarkable for the violence 
of his objections to the Newtonian doctrine. 

There can be no doubt, however, that much 
of the opposition Goethe met with was to be 
attributed to the manner as well as to the sub- 
stance of his statements. Had he contented 
himself with merely detailing his experiments 
and showing their application to the laws of 
chromatic harmony, leaving it to others to re- 
concile them as they could with the pre-estab« 
lished system, or even to doubt in consequence, 
the truth of some of the Newtonian conclusions, 
he would have enjoyed the credit he deserved 
for the accuracy and the utility of his investi- 
gations. As it was, the uncompromising ex- 
pression of his convictions only exposed him to 
the resentment or silent neglect of a great por- 
tion of the scientific world, so that for a time he 
could not even obtain a fair hearing for the less 
objectionable or rather highly valuable commu- 
nications contained in his book. A specimen 
of his manner of alluding to the Newtonian 
theory will be seen in the preface. 

It was quite natural that this spirit should 
call forth a somewhat vindictive feeling, and 
with it not a little uncandid as well as unspar- 
ing criticism. " The Doctrine of Colours" met 



Digitized by 



Google 



X TRANSLATOR'S PREFACE. 

with this reception in Germany long before it 
was noticed in England^ where a milder and 
fairer treatment could hardly be expected, espe- 
cially at a time when, owing perhaps to the 
limited intercourse with the continent, Grerman 
literature was far less popular than it is at pre- 
sent. This last fact, it is true, can be of little 
importance in the present instance, for although 
the change of opinion with regard to the genius 
of an enlightened nation must be acknowledged 
to be beneficial, it is to be hoped there is no 
fashion in science, and the translator begs to 
state once for all, that in advocating the ne- 
glected merits of the ** Doctrine of Ck)lours/' he 
is far from undertaking to defend its imputed 
errors. Sufficient time has, however, now 
elapsed since the publication of this work (in 
1810) to allow a calmer and more candid exami- 
nation of its claims. In this more pleasing task 
Germany has again for some time led the way, 
and many scientific investigators haVe followed 
up the hints and observations of Goethe with a 
due acknowledgment of the acuteness of his 
views.* 

* Sixteen years after the appearance of the Farhenlehre, Dr. 
Johannes MGller devoted a portion of his work, **Zur vergleich- 
enden Physiologie des Gesichtssinnes des Menschen und der 



Digitized by 



Google 



TRANSLATOR'S PREFACE. XI 

It may require more magnanimity in English 
scientific readers to do justice to the merits of 
one who was so open and, in many respects^ 
it is believed, so mistaken an opponent of 
Newton; but it must be admitted that the 
statements of Goethe contain more useful prin- 
ciples in all that relates to harmony of colour 
than any that have been derived from the esta- 
blished doctrine. It is no derogation of the 
more important truths of the Newtonian theory 
to say, that the views it contains seldom appear 
in a form calculated for direct application to the 
arts. The principle of contrast, so universally 
exhibited in nature, so apparent in the action 
and re-action of the eye itself^ is scarcely hinted 
at. The equal pretensions of seven colours, as 



Thiere," to the critical examination of Goethe's theory. In his 
introductory remarks he expresses himself as follows — ^** For my 
own part I readily acknowledge that I have been greatly indebted 
to Goethe's treatise, and can truly say that without having studied 
it for some years in connexion with the actual phenomena, the pre- 
sent work would hardly have been undertaken. I have no hesitation 
in confessing more particularly that I have full faith in Goethe's 
statements, where they are merely descriptive of the phenomena, 
and where the author does not enter into explanations involving 
a decision on the great points of controversy." The names of 
Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and 
many others might be added, as authorities more or less favourable 
to the Farbenlehre. 



Digitized by 



Google 



XII TRANSLATOR'S PREFACE. 

such, and the fanciful analogies which their 
assumed proportions could suggest, have rarely 
found favour with the votaries of taste, — indeed 
they have long been abandoned even by 
scientific authorities.* And here the trans- 
lator stops : he is quite aware that the defects 
which make the Newtonian theory so little 
available for aesthetic application, are far from 
invalidating its more important conclusions in 
the opinion of most scientific men. In carefully 
abstaining therefore from any comparison be- 
tween the two theories in these latter respects, 
he may still be permitted to advocate the clear- 
ness and fulness of Goethe's experiments. The 
German philosopher reduces the colours to their 



* ** When Newton attempted to reckon up the rays of light 
decomposed by the prism," says Sir John Leslie, ** and ventured 
to assign the famous number sevens he was apparently influenced 
' by some lurking disposition towards mysticism. If any unpreju- 
diced person will fietirly repeat the experiment, he must soon be 
convinced that the various coloured spaces which paint the spec- 
trum slide into each other by indefinite shadings : he may name 
four or five principal colours, but the subordinate spaces are evi- 
dently so multiplied as to be incapable of enumeration. The 
same illustrious mathematician, we can hardly doubt, was be- 
trayed by a passion for analogy, when he imagined that the pri- 
mary colours are distributed over the spectrum after the proportions 
of the diatonic scale of music, since those intermediate spaces have 
really no precise and defined limits." — Treatises on Varimu 
Subjects of Natural and Chemical Philosophy, p. 59. 



Digitized by 



Google 



TRANSLATOR'S PREFACE. XlU 

origin and simplest elements ; he sees and con- 
stantly bears in mind, and sometimes ably 
elucidates, the phenomena of contrast and gra- 
dation, two principles which may be said to 
make up the artist's world, and to constitute the 
chief elements of beauty. These hints occur 
mostly in what may be called the scientific part 
of the work. On the other hand, in the portion 
expressly devoted to the aesthetic application of 
the doctrine, the author seems to have made but 
an inadequate use of his own principles. 

In that part of the chapter on chemical co- 
lours which relates to the colours of plants and 
animals, the same genius and originality which 
are displayed in the Essays on Morphology, and 
which have secured to Groethe undisputed rank 
among the investigators of nature, are frequently 
apparent. 

Bat one of the most interesting features of 
Goethe's theory, although it cannot be a recom- 
mendation in a scientific point of view, is, that 
it contains, undoubtedly with very great im- 
provements, the general doctrine of the ancients 
and of the Italians at the revival of letters. 
The translator has endeavoured, in some notes, 
to point out the connexion between this theory 
and the practice of the Italian painters. 



Digitized by 



Google 



XIV TRANSLATOR'S PREFACE. 

The " Doctrine of Colours/' as first published 
in 1810» consists of two volumes in 8vo., and 
sixteen plates, with descriptions, in 4to. It is 
divided into three parts^ a didactic, a contro- 
versial, and ah historical part; the present 
translation is confined to the first of these, with 
such extracts from the other two as seemed 
necessary, in fairness to the author, to explain 
some of his statements. The polemical and 
historical parts are frequently alluded to in the 
preface and elsewhere in the present work, but 
it has not been thought advisable to omit these 
allusions. No alterations whatever seem to 
have been made by Goethe in the didactic por- 
tion in later editions, but he subsequently wrote 
an additional chapter on entoptic colours, ex- 
pressing his wish that it might be inserted in 
the theory itself at a particular place which he 
points out. The form of this additional essay 
is, however, very diflferent from that of the rest 
of the work, and the translator has therefore 
merely given some extracts from it in the ap- 
pendix. The polemical portion has been more 
than once omitted in later editions. 

In the two first parts the author's statements 
are arranged numerically, in the style of Bacon's 
Natural History. This, we are told, was for the 



Digitized by 



Google 



TRANSLATOR'S PREFACE. XV 

convenience of reference; but many passages 
are thus separately numbered which hardly 
seem to have required it. The same arrange- 
ment is, however, strictly followed in the trans- 
lation to facilitate a comparison with the original 
where it may be desired ; and here the translator 
observes, that although he has sometimes per- 
mitted himself to make slight alterations^ in 
order to avoid unnecessary repetition, or to 
make the author's meaning clearer, he feels 
that an apology may rather be expected from 
him for having omitted so little. He was scru- 
pulous on this point, having once determined to 
translate the whole treatise, partly, as before 
stated, from a wish to deal fairly with a con- 
troversial writer, and partly because many pas- 
sages, not directly bearing on the scientific 
views^ are still characteristic of Goethe. The 
observations which the translator has ventured 
to add are inserted in the appendix : these ob- 
servations are chiefly confined to such of the 
author's opinions and conclusions as have direct 
reference to the arts ; they seldom interfere with 
the scientific propositions, even where these 
have been considered most vulnerable. 



Digitized by 



Google 



Digitized by 



Google 



PREFACE TO THE FIRST EDITION 

OP 1810- 



It may naturally be asked whether, in proposing 
to treat of colours, light itself should not first 
engage our attention : to this we briefly and 
frankly answer that since so much has already 
been said on the subject of light, it can hardly 
be desirable to multiply repetitions by again 
going over the same ground. 

Indeed, strictly speaking, it is useless to at- 
tempt to express the nature of a thing abstract- 
edly. Efiects we can perceive, and a complete 
history of those efiects would, in fact, sufficiently 
define the nature of the thing itself. We should 
try in vain to describe a man's character, but let 
his acts be collected and an idea of the character 
will be presented to us. 

The colours are acts of light ; its active and 
passive m.odifications : thus considered we may 
expect from them some explanation respecting 
light itself. Colours and light, it is true, stand 
in the most intimate relation to each other, but 

b 



Digitized by 



Google 



XVlll PREFACE TO THE FIRST EDITION. 

we should think of both as belonging to nature 
as a whole^ for it is nature as a whole which 
manifests itself by their means in an especial 
manner to the sense of sight. 

The completeness of nature displays itself to 
another sense in a similar way. Let the eye be 
closed, let the sense of hearing be excited, and 
from the lightest breath to the wildest din, from 
the simplest sound to the highest harmony, 
from the most vehement and impassioned cry 
to the gentlest word of reason, still it is Nature 
that speaks and manifests her presence, her 
power, her pervading life and the vastness of 
her relations ; so that a blind man to whom the 
infinite visible is denied^ can still comprehend 
an infinite vitality by means of another organ. 

And thus as we descend the scale of beings 
Nature speaks to other senses — to known, mis- 
understood, and unknown senses : so speaks she 
with herself and to us in a thousand modes. To 
the attentive observer she is nowhere dead nor 
silent ; she has even a secret agent in inflexible 
matter, in a metal, the smallest portions of which 
tell us what is passing in the entire mass. How- 
ever manifold, complicated, and unintelligible 
this language may often seem to us, yet its ele- 
ments remain ever the same. With light poise 



Digitized by 



Google 



PREFACE TO THE FIRST EDITION. XIX 

and coanterpoise, Nature oscillates within her 
prescribed limits, yet thus arise all the varieties 
and conditions of the phenomena which are 
presented to us in space and time. 

Infinitely various are the means by which we 
become acquainted with these general move- 
ments and tendencies : now as a simple repul- 
sion and attraction, now as an upsparkling and 
vanishing light, as undulation in the air, as com- 
motion in matter, as oxydation and deoxydation ; 
but always, uniting or separating, the great pur- 
pose is found to be to excite and promote exist- 
ence in some form or other. 

The observers of nature finding, however, 
that this poise and count^poise are respectively 
unequal in efiect, have endeavoured to repre- 
sent such a relation in terms. They have every- 
where remarked and spoken of a greater and 
lesser principle, an action and resistance, a 
doing and suffering, an advancing and retiring, 
a violent and moderating power; and thus a 
symbolical language has arisen, which, from 
its close analogy, may be employed as equiva- 
lent to a direct and appropriate terminology. 

To apply these designations, this language of 
Nature to the subject we have undertaken ; to 
enrich and amplify this language by means of 

b2 



Digitized by 



Google 



XX PREFACE TO THE FIRST EDITION. 

the theory of colours and the variety of their 
phenomena, and thus facilitate the communica- 
tion of higher theoretical views, was the prin- 
cipal aim of the present treatise. 

The work itself is divided into three parts. 
The first contains the outline of a theory of 
colours. In this, the innumerable cases which 
present themselves to the observer are collected 
under certain leading phenomena, according to 
an arrangement which will be explained in the 
Introduction ; and here it may be remarked, that 
although we have adhered throughout to experi- 
ment, and throughout considered it as our basis, 
yet the theoretical views which led to the ar- 
rangement alluded to, could not but be stated. 
It is sometimes unreasonably required by per- 
sons who do not even themselves attend to 
such a condition, that experimental information 
should be submitted without any connecting 
theory to the reader or scholar, who is himself 
to form his conclusions as he may list. Surely 
the mere inspection of a subject can profit us 
but little. Every act of seeing leads to consi- 
deration, consideration to reflection, reflection 
to combination, and thus it may be said that in 
every attentive look on nature we already theo- 
rise. But in order to guard against the possible 



Digitized by 



Google 



PREFACE TO THE FIRST EDITION. XXI 

abuse of this abstract view, in order that the 
practical deductions we look to should be really 
useful, we should theorise without forgetting 
that we are so doing, we should theorise with 
mental self-possession, and, to use a bold word, 
with irony. 

In the second part* we examine the New- 
tonian theory ; a theory which by its ascend- 
ancy and consideration has hitherto impeded a 
free inquiry into the phenomena of colours. We 
combat that hypothesis, for although it is no 
longer found available, it still retains a tradi- 
tional authority in the world. Its real relations 
to its subject will require to be plainly pointed 
out ; the old errors must be cleared away, if the 
theory of colours is not still to remain in the rear 
of so many other better investigated depart- 
ments of natural science. Since, however, this 
second part of our work may appear somewhat 
dry as regards its matter, and perhaps too vehe- 
ment and excited in its manner, we may here 
be permitted to introduce a sort of allegory in 
a lighter style, as a prelude to that graver por- 
tion, and as some excuse for the earnestness 
alluded to. 

We compare the Newtonian theory of colours 

* The Polemical part. 



Digitized by 



Google 



XXII PREFACE TO THE FIRST EDITION. 

to an old castle, which was at first constructed 
by its architect with youthful precipitation ; it 
was, however, gradually enlarged and equipped 
by him according to the exigencies of time and 
circumstances, and moreover was still further 
fortified and secured in consequence of feuds 
and hostile demonstrations. 

The same system was pursued by his succes- 
sors and heirs : their increased wants within, 
the harassing vigilance of their opponents with- 
out, and various accidents compelled them in 
some places to build near, in others in con- 
nexion with the fabric, and thus to extend the 
original plan. 

It became necessary to connect all these in- 
congruous parts and additions by the strangest 
galleries, halls and passages. All damages, 
whether inflicted by the hand of the enemy or 
the power of time, were quickly made good. As 
occasion required, they deepened the moats, 
raised the walls, and took care there should be 
no lack of towers, battlements, and embrasures. 
This care and these exertions gave rise to a pre- 
judice in favour of the great importance of the 
fortress, and still upheld that prejudice, although 
the arts of building and fortification were by 
this time very much advanced, and people had 



Digitized by 



Google 



PBEFACE TO THE FIRST EDITION. XXlIl 

learnt to construct much better dwellings and 
defences in other cases. But the old castle 
was chiefly held in honour because it had 
never been taken, because it had repulsed so 
many assaults, had baffled so many hostile 
operations, and had always preserved its vii^in 
renown. This renown, this influence lasts even 
now : it occurs to no one that the old castle is 
become uninhabitable. Its great duration, its 
costly construction, are still constantly spoken 
ot Pilgrims wend their way to it ; hasty 
sketches of it are shown in all schools, and it is 
thus recommended to the reverence of suscep- 
tible youth. Meanwhile, the building itself is 
already abandoned ; its only inmates are a few 
invalids, who in simple seriousness imagine that 
they are prepared for war. 

Thus there is no question here respecting a 
tedious siege or a doubtful war ; so far from it 
we find this eighth wonder of the world already 
nodding to its fall as a deserted piece of anti- 
quity, and begin at once, without further cere- 
mony, to dismantle it from gable and roof 
downwards ; that the sun ipay at last shine into 
the old nest of rats and owls, and exhibit to the 
eye of the wondering traveller that labyrinthine, 
incongruous style of building, with its scanty, 



Digitized by 



Google 



XXlV PREFACE TO THE FIRST EDITION. 

make-shift contrivances, the result of accident 
and emergency, its intentional artifice and 
clumsy repairs. Such an inspection will, how- 
ever, only be possible when wall after wall, arch 
after arch, is demolished, the rubbish being at 
once cleared away as well as it can be. 

To effect this, and to level the site where it is 
possible to do so, to arrange the materials thus 
acquired, so that they can be hereafter again 
employed for a new building, is the arduous 
duty we have undertaken in this Second Part. 
Should we succeed, by a cheerful application of 
all possible ability and dexterity, in razing this 
Bastille, and in gaining a free space, it is thus 
by no means intended at once to cover the site 
again and to encumber it with a new structure ; 
we propose rather to make use of this area for 
the purpose of passing in review a pleasing and 
varied series of illustrative figures. 

The third part is thus devoted to the histo- 
rical account of early inquirers and investiga- 
tors. As we before expressed the opinion that 
the history of an individual displays his cha- 
racter, so it may here be well affirmed that the 
history of science is science itself. We cannot 
clearly be aware of what we possess till we have 
the means of knowing what others possessed 



Digitized by 



Google 



PREFACE TO THE FIRST EDITION. XXY 

before us. We cannot really and honestly re- 
joice in the advantages of our own time if we 
know not how to appreciate the advantages of 
former periods. But it was impossible to write, 
or even to prepare the way for a history of the 
theory of colours while the Newtonian theory 
existed; for no aristocratic presumption has 
ever looked down on those who were not of its 
order, with such intolerable arrogance as that 
betrayed by the Newtonian school in deciding 
on all that had been done in earlier times and 
all that was done around it. With disgust and 
indignation we find Priestley, in his History of 
Optics, like many before and after him, dating 
the success of all researches into the world of 
colours from the epoch of a decomposed ray 
of light, or what pretended to be so ; looking 
down with a supercilious air on the ancient and 
less modern inquirers, who, after all, had pro- 
ceeded quietly in the right road, and who have 
transmitted to us observations and thoughts in 
detail which we can neither arrange better nor 
conceive more justly. 

We have a right to expect from one who pro- 
poses to give the history of any science, that he 
inform us how the phenomena of which it treats 
were gradually known, and what was imagined, 



Digitized by 



Google 



XXYl PBBFACE TO THE FIRST EDITION. 

conjectured, assumed, or thought respecting 
them. To state all this in due connexion is by 
no means an easy task ; need we say that to 
write a history at all is always a hazardous 
affair; with the most honest intention there is 
always a danger of being dishonest; for in such 
an undertaking, a writer tacitly announces at 
the outset that he means to place some things 
in light, others in shade. The author has, 
nevertheless, long derived pleasure from the 
prosecution of his task : but as it is the in- 
tention only that presents itself to the mind 
as a whole, while the execution is gene- 
rally accomplished portion by portion, he is 
compelled to admit that instead of a history 
he furnishes only materials for one. These 
materials consist in translations, extracts, ori- 
ginal and borrowed comments, hints, and notes; 
a collection, in short, which, if not answering 
all that is required, has at least the merit of 
having been made with earnestness and inte- 
rest Lastly, such materials, — not altogether 
untouched it is true, but still not exhausted, — 
may be more satisfactory to the reflecting reader 
in the state in which they are, as he can easily 
combine them according to his own judgment. 
This third part, containing the history of the 



Digitized by 



Google 



PBBFACE TO THE FIRST EDITION. XXVll 

science, does not, however, thus conclude the 
subject: a fourth supplementary portion^ is 
added. This contains a recapitulation or revi- 
sion ; with a view to which, chiefly, the para- 
graphs are headed numerically. In the execu- 
tion of a work of this kind some things may be 
forgotten, some are of necessity omitted, so as 
not to distract the attention, some can only be 
arrived at as corollaries, and others may require 
to be exemplified and verified : on all these ac- 
counts, postscripts, additions and corrections 
are indispensable. This part contains, besides, 
some detached essays ; for example, that on the 
atmospheric colours; for as these are introduced 
in the theory itself without any classification, 
they are here presented to the mind's eye at 
one view. Again, if this essay invites the reader 
to consult Nature herself, another is intended to 
recommend the artificial aids of science by cir- 
cumstantially describing the apparatus which 
will in future be necessar}"^ to assist researches 
into the theory of colours. 
In conclusion, it only remains to speak of the 



* This preface must have been written before the work was 
finished, for at the conclusion of the historical part there is only 
an apology for the non-appearance of the supplement here al- 
luded to. 



Digitized by 



Google 



XXVm PREFACE TO THE FIRST EDITION. 

plates which are added at the end of the work;* 
and here we confess we are reminded of that 
incompleteness and imperfection which the 
present undertaking has, in common with all 
others of its class ; for as a good play can be in 
fact only half transmitted to writing, a great 
part of its effect depending on the scene, the 
personal qualities of the actor, the powers of 
his voice, the peculiarities of his gestures, and 
even the spirit and favourable humour of the 
spectators; so it is, in a still greater degree, 
with a book which treats of the appearances of 
nature. To be enjoyed, to be turned to account. 
Nature herself must be present to the reader, 
either really, or by the help of a lively imagina- 
tion. Indeed, the author should in such cases 
communicate his observations orally, exhibiting 
the phenomena he describes — as a text, in the 
first instance, — partly as they appear to us un- 
sought, partly as they may be presented by 
contrivance to serve in particular illustration. 
Explanation and description could not then fail 
to produce a lively impression. 

The plates which generally accompany works 
like the present are thus a most inadequate sub- 

* In the present translation the necessary plates accompany 
the text. 



Digitized by 



Google 



PREFACE TO THE FIRST EDITION. XXIX 

stitute for all this; a physical phenomenon 
exhibiting its effects on all sides is not to be 
arrested in lines nor denoted by a section. No 
one ever dreams of explaining chemical expe- 
riments with figures ; yet it is customary in 
physical researches nearly allied to these, be- 
cause the object is thus found to be in some 
degree answered. In many cases, however, such 
diagrams represent mere notions ; they are sym- 
bolical resources, hieroglyphic modes of com- 
munication, which by degrees assume the place 
of the phenomena and of Nature herself, and 
thus rather hinder than promote true know- 
ledge. In the present instance we could not 
dispense with plates, but we have endeavoured 
so to construct them that they may be confi- 
dently referred to for the explanation of the 
didactic and polemical portions. Some of these 
may even be considered as forming part of the 
apparatus before mentioned. 

We now therefore refer the reader to the 
work itself; first, only repeating a request 
which many an author has already made in 
vain, and which the modern German reader, 
especially, so seldom grants: — 

Si quid novisti rectius istis 
Candidus imperti ; si noD, his utere mecunu 



Digitized by 



Google 



DIRECTIONS FOR PLACING THE PLATES. 



Plate 1 to face page .6 

2 ditto . . .82 

3 ditto . .107 

4 ditto . . .136 



Digitized by 



Google 



CONTENTS. 



PAOB 

Introduction .... xxxvii 



PART I. 
PHYSIOLOGICAL COLOURS. 

I. Effects of Light and Darkness on the Eye . 2 

II. Effects of Black and White Objects on the Eye 5 

III. Grey Surfaces and Objects . . 14 

IV. Dazzling Colourless Objects . • . 16 
V. Coloured Objecto . . .20 

VI. Coloured Shadows . . . 29 

VII. Faint Lights . . .38 

VIII. Subjective Halos . . . . 40 

Pathological Colours — ^Appendix . . 45 

PART II. 
PHYSICAL COLOURS. 

IX. Dioptrical Colours . . . 59 
X. Dioptrical Colours of the Furst Class . 60 
XI. Dioptrical Colours of the Second Class — Re- 
fraction . . . . 74 
Subjectiye Experiments . • .80 
XII. Refraction without the Appearance of Colour ib. 

XIII. Conditions of the Appearance of Colour • 81 

XIV. Conditions under which the Appearance of Co- 

lour increases . . .86 

XV. Explanation of the foregoing Phenomena . 90 

XVI. Decrease of the Appearance of Colour • 100 

XVII. Grey Objects displaced by Refraction . , 103 

XVIII. Coloured Objects displaced by Refraction . 106 

XIX. Achromatism and Hyperchromatism . 118 



Digitized by 



Google 



xxxu 



CONTENTS. 



XX. Advantages of Subjective Experiments — 

Transition to the Objective 

Objective Esperiments 

XXI. Refraction without the Appearance of Colour 

XXI I. Conditions of the Appearance of Colour 

XXIII. Conditions of the Increase of Colour 

XXIV. Explanation of the foregoing Phenomena 
XXV. Decrease of the Appearance of Colour 

XXVI. Grey ObjecU 
XXVII. Coloured ObjecU 
XXVIII. Achromatism and Hyperchromatism 
XXIX. Combination of Subjective and Objective Ex- 

periments 
XXX. Transition 
XXXI. Catoptrical Colours 
XXXI 1. Paroptical Colours 

XXXIII. Epoptical Colours 

PART III. 
CHEMICAL COLOURS. 

XXXIV. Chemical Contrast . 
XXXV. White 

XXXVI. Black 
XXXVII. First Excitation of Colour 
XXXVIII. Augmentation of Colour 
XXXIX. Culmination . 
XL. Fluctuation 

XLI. Passage through the Whole Scale 
XLII. Inversion 
XLI II. Fixation 
XLIV. Intermixture^ Real 
XLV. Intermixture, Apparent 
XLVI. Communication, Actual 
XLVII. Communication, Apparent 
XLVIII. Extraction 
XLIX. Nomenclature . 



123 
125 
121 
128 
134 
139 
141 
142 
143 
145 

147 
150 
154 
163 

171 



202 
203 
205 
206 
212 
214 
217 
218 
220 
221 
223 
226 
230 
235 
237 
242 



Digitized by 



Google 



CONTENTS. XXXlll 

fAOE 

^L. MmeralB • . , . 245 

LI. Plants • • , , • 247 

LII. Wonns, Insects, Fishes . . 252 

LIII. Birds . . . . . 259 

LIV. Mammalia and Human Beings • . 262 

LV. Physical and Chemical ££fects of the Transmission 

of Light through Coloured Mediums • • 266 

LVI. Chemical Effect in Dioptrical Achromatism • 2*70 

PART IV. 
GENERAL CHABACTERI8TIC8, 

The Facility with which Colour appears • « 274 

The Definite Nature of Colour . . . 276 

Combination of the Two Principles . . . 277 

Augmentation to Red • • • • ib. 

Junction of the Two Augmented Extremes • . 278 

Completeness the Result of Variety in Colour « • 279 

Harmony of the Complete State . . . 280 
Facility with which Colour may be made to tend either to 

the Plus or Minus side . .281 

Evanescence of Colour . . . . ib. 

Permanence of Colour . . . « 282 

PART V. 
RELATION TO OTHER PURSUITS. 

Relation to Philosophy • . • . 283 

Rdation to Mathematics • . • « 286 

Relation to the Technical Operations of the Dyer • 289 

Relation to Physiology and Pathol(^y . . 291 

Relation to Natural History . 292 

Relation to General Physics . . . • 293 

Relation to the Theory of Music . • • 298 

Concluding Observations on Terminulc^y • • 300 

PART VI. 

EFFECT OF COLOUR WITH REFERENCE TO MORAL 
ASSOCIATIONS. 

Yellow . • . .306 

C 



Digitized by 



Google 



XXXIV CONTENTS. 






PAGE 


Red-Yellow . . . . . 


308 


Yellow-Red .... 


309 


Blue . . . . . 


310 


Red-Blue ..... 


312 


Blue-Red . . . . 


313 


Red .... . 


ib. 


Green , . . . . 


316 


Completeness and Harmony 


ib. 


Characteristic Combinations . . • . 


321 


Yellow and Blue .... 


322 


Yellow and Red . . . . 


ib. 


Blue and Red .... 


ib. 


Yellow-Red and Blue-Red . . . 


323 


Combinations Non -Characteristic . 


324 


Relation of the Combinations to Light and Dark 


325 


Considerations derived from the Evidence of Experience 




and History .... 


326 


iEsthetic Influence . . . 


330 


Chiaro-Scuro .... 


331 


Tendency to Colour . . . . 


334 


Keeping ..... 


335 


Colouring • . . . . 


337 


Colour in General Nature 


ib. 


Colour of Particular Objects . . . . 


338 


Characteristic Colouring 


339 


Harmonious Colouring . . . 


341 


Genuine Tone . . . . 


342 


False Tone . . . . 


ib. 


Weak Colouring .... 


343 


The Motley . . . . 


344 


Dread of Theory . . . . 


ib. 


Ultimate Aim . . . . . 


345 


Grounds ..... 


ib. 


Pigments . . . . 


348 


Allegorical, Symbolical, Mystical Application of Colour . 


350 


Concluding Observations 


352 



Digitized by 



Google 



OUTLINE 



THEORY OF COLOURS. 



** Si Tera nostra sunt aut falsa, enint talia, licet nostra per Titam defen- 
dimus. ' Post &ta nostra pueri qui niinc ludunt nostri Judices enint." 



c 2 



Digitized by 



Google 



Digitized by 



Google 



INTRODUCTION, 



The desire of knowledge is first stimulated id us 
when remarkable phenomena attract our atten* 
tion. In order that this attention be continued, 
it is necessary that we should feel some interest 
in exercising it, and thus by degrees we become 
better acquainted with the object of our curi- 
osity* During this process of observation we 
remark at first only a vast variety which presses 
indiscriminately on our view ; we are forced to 
separate, to distinguish, and again to combine ; 
by which means at last a certain order arises 
which admits of being surveyed with more or 
less satisfaction. 

To accomplish this, only in a certain degree, 
in any department, requires an unremitting and 
close application ; and we find, for this reason^ 
that men prefer substituting a general theore** 
tical view, or some system of explanation, for 
the facts themselves, instead of taking the trou^ 
ble to make themselves first acquainted with 
cases in detail and then constructing a whole. 

The attempt to describe and class the phe- 
nomena of colours has been only twice made : 
first by Theophrastus,* and in modern times by 

* The treatise to which the author alludes ib more generally 
ascribed to Aristotle. — T. 



Digitized by 



Google 



XXXVIU INTRODUCTION. 

Boyle. The pretensions of the present essay 
to the third place will hardly be disputed. 

Our historical survey enters into further de- 
tails. Here we merely observe that in the last 
century such a classification was not to be 
thought of» because Newton had based his hypo- 
thesis on a phenomenon exhibited in a compli- 
cated and secondary state ; and to this the other 
cases that forced themselves on the attention 
were contrived to be referred, when they could 
not be passed over in silence; just as an astro- 
nomer would do, if from whim he were to place 
the moon in the centre of our system ; he would 
be compelled to make the earth, sun, and pla- 
nets revolve round the lesser body, and be forced 
to disguise and gloss over the error of his first 
assumption by ingenious calculations and plau- 
sible statements. 

In our prefatory observations we assumed the 
reader to be acquainted with what was known 
respecting light ; here we assume the same with 
regard to the eye. We observed that all nature 
manifests itself by means of colours to the sense 
of sight. We now assert,, extraordinary as it 
may in some degree appear, that the eye sees 
no form, inasmuch as light, shade, and colour 
together constitute that which to our vision dis- 
tinguishes object from object, and the parts of 
an object from each other. From these three, 
light, shade, and colour, we construct the visible 



Digitized by 



Google 



INTRODUCTION. XXXIX 

world, and thus, at the same time, make paint- 
ing possible, an art which has the power of 
producing on a flat surface a much more perfect 
▼isible world than the actual one can be. 

The eye may be said to owe its existence to 
light, which calls forth, as it were, a sense that 
is akin to itself; the eye, in short, is formed 
with reference to light, to be fit for the acticm 
of light ; the light it contains corresponding with 
the light without 

We are here reminded of a significant adage 
in constant use with the ancient Ionian school-^ 
" Like is only known by Like ;'* and again, of 
the words of an old mystic writer, which may 
be thus rendered, '* If the eye were not sunny, 
how could we perceive light? If God's own 
strength lived not in us, how could we delight 
in Divine things?" This immediate affinity 
between light and the eye will be denied by 
none; to consider them as identical in sub- 
stance is less easy to comprehend. It will be 
more intelligible to assert that a dormant 
light resides in the eye, and that it may be ex- 
cited by the slightest cause fi'om within or from 
without. In darkness we can, by an efibrt of 
imagination, call up the brightest images; in 
dreams objects appear to us as in broad day- 
light; awake, the slightest external action of 
light is perceptible, and if the organ suffers an 
actual shock, light and colours spring forth. 



Digitized by 



Google 



Xi INTRODUCTION. 

Here, however, those who are wont to proceed 
according to a certain method^ may perhaps 
observe that as yet we have not decidedly ex- 
plained what colour is. This question, like the 
definition of light and the eye, we would for the 
present evade, and would appeal to our inquiry 
itself, where we have circumstantially shown 
how colour is produced. We have only there- 
fore to repeat that colour is a law of nature in 
relation with the sense of sight. We must as« 
sume, too, that every one has this sense, that 
every one knows the operation of nature on it, 
for to a blind man it would be impossible to 
speak of colours. 

That we may not, however, appear too anxious 
to shun such an explanation, we would re-state 
what has been said as follows: colour is an 
elementary phenomenon in nature adapted to 
the sense of vision ; a phenomenon which, like 
all others, exhibits itself by separation and con- 
trast^ by commixture and union, by augmenta- 
tion and neutralization, by communication and 
dissolution : under these general terms its 
nature may be best comprehended. 

We do not press this mode of stating the sub- 
ject on any one. Those who, like ourselves, 
find it convenient, will readily adopt it ; but we 
have no desire to enter the lists hereafter in 
its defence. From time immemorial it has been 
dangerous to treat of colour ; so much so, that 



Digitized by 



Google 



INTRODUCTION. xU 

one of our predecessors ventured on a certain 
occasion to say, *'The ox becomes furious 
if a red cloth is shown to him ; but the philo- 
sopher, who speaks of colour only in a general 
way, begins to rave." 

Nevertheless, if we are to proceed to give 
some account of our work, to which we have 
appealed, we must begin by explaining how 
we have classed the different conditions under 
which colour is produced. We found three 
modes in which it appears; three classes of 
colours, or rather three exhibitions of them 
all. The distinctions of these classes are easily 
expressed. 

Thus, in the first instance, we considered co- 
lours^ as far as they may be said to belong to 
the eye itself, and to depend on an action and 
re-action of the organ ; next, they attracted our 
attention as perceived in, or by means of, colour- 
less mediums ; and lastly, where we could con- 
sider them as belonging to particular substances. 
We have denominated the first, physiological, 
the second, physical, the third, chemical colours. 
The first are fleeting and not to be arrested; 
the next are passing, but still for a while en-^ 
during; the last may be made permanent for 
any length of time. 

Having separated these classes and kept them 
as distinct as possible, with a view to a clear, 
didactic exposition, we have been enabled at 



Digitized by 



Google 



Xlii INTRODUCTION. 

the same time to exhibit them in an unbroken 
series, to connect the fleeting with the somewhat 
more enduring, and these again with the per* 
manent hues ; and thus, after having carefully 
attended to a distinct classification in the first 
instance, to do away with it again when a larger 
view was desirable. 

In a fourth division of our work we have 
therefore treated generally what was previously 
detailed under various particular conditions, 
and have thus, in fact, given a sketch for a 
future theory of colours. We will here only an- 
ticipate our statements so far as to observe, that 
light and darkness, brightness and obscurity^ or 
if a more general expression is preferred, light 
and its absence, are necessary to the production 
of colour. Next to the light, a colour appears 
which we call yellow ; another appears next to 
the darkness, which we name blue. When 
these, in their purest state, are so mixed that 
they are exactly equal, they produce a third 
colour called green. Each of the two first^named 
colours can however of itself produce a new tint 
by being condensed or darkened. They thus 
acquire a reddish appearance which can be in- 
creased to so great a degree that the original 
blue or yellow is hardly to be recognised in it : 
but the intensest and purest red, especially in 
physical cases, is produced when the two ex- 
tremes of the yellow-red and blue-red are 



Digitized by 



Google 



mTROj)ucTioN. xliii 

united. This is the actual state of the appear- 
ance and generation of colours. But we can 
also assume an existing red in addition to the 
definite existing blue and yellow> and we can pro- 
duce contrariwise, by mixing, what we directly 
produced by augmentation or deepening. With 
these three or six colours, which may be con- 
veniently included in a circle, the elementary 
doctrine of colours is alone concerned. All 
other modifications, which may be extended to 
infinity, have reference more to the application, — 
have reference to the technical operations of the 
painter and dyer, and the various purposes of 
artificial life. To point out another general 
quality, we may observe that colours throughout 
are to be considered as half-lights, as half- 
shadows, on which account if they are so mixed 
as reciprocally to destroy their specific hues, a 
shadowy tint, a grey, is produced. 

In the fifth division of our inquiry we had 
proposed to point out the relations in which we 
should wish our doctrine of colours to stand 
to other pursuits. Important as this part of our 
work is, it is perhaps on this very account not 
so successful as we could wish. Yet when we 
reflect that strictly speaking these relations 
cannot be described before they exist, we may 
console ourselves if we have in some degree 
failed in endeavouring for the first time to 
define them. For undoubtedly we should first 



Digitized by 



Google 



Xliv INTRODUCTION. 

wait to see how those whom we have endea- 
voured to serve, to whom we have intended to 
make an agreeable and useful offering, how such 
persons, we say, will accept the result of our 
utmost exertion : whether they will adopt it, 
whether they will make use of it and follow it 
up, or whether they will repel, reject, and suffer 
it to remain unassisted and neglected. 

Meanwhile, we venture to express what we 
believe and hope. From the philosopher we 
believe we merit thanks for having traced the 
phenomena of colours to their first sources, to 
the circumstances under which they simply 
appear and are, and beyond which no further 
explanation respecting them is possible. It will, 
besides, be gratifying to him that we have ar- 
ranged the appearances described in a form that 
admits of being easily surveyed, even should he 
not altogether approve of the arrangement itself. 

The medical practitioner, especially him 
whose study it is to watch over the organ of 
sight, to preserve it, to assist its defects and 
to cure its disorders, we reckon to make espe- 
cially our friend. In the chapter on the phy- 
siological colours, in the Appendix relating to 
those that are more strictly pathological, he will 
find himself quite in his own province. We are 
not without hopes of seeing the physiological 
phenomena, — a hitherto neglected, and, we may 
add, most important branch of the theory of 



Digitized by 



Google 



INTRODUCTION* xlv 

colours, — completely investigated through the 
exertions of those individuals who in our own 
times are treating this department with success. 

The investigator of nature should receive us 
cordially, since we enable him to exhibit the 
doctrine of colours in the series of other ele- 
mentary phenomena, and at the same time 
enable him to make use of a corresponding no- 
menclature, nay, almost the same words and 
designations as under the other rubrics. It is 
true we give him rather more trouble as a 
teacher, for the chapter of colours is not now to 
be dismissed as heretofore with a few paragraphs 
and experiments ; nor will the scholar submit 
to be so scantily entertained as he has hitherto 
been, without murmuring* On the other hand, 
an advantage will afterwards arise out of this : 
for if the Newtonian doctrine was easily learnt, 
insurmountable difficulties presented themselvse 
in its application. Our theory is perhaps more 
difficult to comprehend, but once known, all is 
accomplished, for it carries its application along 
with it. 

The chemist who looks upon colours as indi- 
cations by which he may detect the more secret 
properties of material things, has hitherto found 
much inconvenience in the denomination and 
description of colours ; nay, some have been in- 
duced after closer and nicer examination to look 
upon colour as an uncertain and fallacious cri- 



Digitized by 



Google 



Xlvi INTRODUCTION. 

terion in chemical operations. Yet we hope by 
means of our arrangement and the nomenclature 
before alluded to, to bring colour again into 
credit, and to awaken the conviction that a pro- 
gressive, augmenting, mutable quality, a quality 
which admits of alteration even to inversion, is 
not fallacious, but rather calculated to bring to 
light the most delicate operations of nature. 

In looking a little further round us, we are not 
without fears that we may fail to satisfy another 
class of scientific men. By an extraordinary com- 
bination of circumstances the theory of colours 
has been drawn into the province and before 
the tribunal of the mathematician, a tribunal to 
which it cannot be said to be amenable. This 
was owing to its afiinity with the other laws of 
vision which the mathematician was legitimately 
calledjUpon to treat. It was owing, again, to 
another circumstance: a great mathematician 
had investigated the theory of colours, and 
having been mistaken in his observations as an 
experimentalist, he employed the whole force of 
his talent to give consistency to this mistake. 
Were both these circumstances considered, all 
misunderstanding would presently be removed, 
and the mathematician would willingly co- 
operate with us, especially in the physical de- 
partment of the theory. 

To the practical man, to the dyer, on the 
other hand, our labour must be altogether ac« 



Digitized by 



Google 



INTRODUCTION. xlvii 

ceptable ; for it was precisely those who re- 
flected on the facts resulting from the opera- 
tions of dyeing who were the least satisfied with 
the old theory : they were the first who per- 
ceived the insufficiency of the Newtonian doc- 
trine. The conclusions of men are very different 
according to the mode in which they approach 
a science or branch of knowledge ; from which 
side, through which door they enter. The 
literally practical man, the manufacturer, whose 
attention is constantly and forcibly called to the 
facts which occur under his eye, who experiences 
benefit or detriment from the application of his 
convictions, to whom loss of time and money is 
not indifierent, who is desirous of advancing, 
who aims at equalling or surpassing what others 
have accomplished, — such a person feels the 
unsoundness and erroneousness of a theory 
much sooner than the man of letters, in whose 
eyes words consecrated by authority are at last 
equivalent to solid coin ; than the mathematician, 
whose formula always remains infallible, even 
although the foundation on which it is con- 
structed may not square with it. Again, to 
carry on the figure before employed, in entering 
this theory from the side of painting, from the 
side of aesthetic* colouring generally, we shall be 



* iEsthetic — belonging to taste as mere internal sense, from 
alaOdyofiaif to feel ; the word was first used by Wolf. — ^T. 



Digitized by 



Google 



Xlviii INTRODUCTION. 

found to have accomplished a most thankworthy 
office for the artist. In the sixth part we have 
endeavoured to define the effects of colour as ad- 
dressed at once to the eye and mind, with a view 
to making them more available for the purposes 
of art. Although much in this portion, and in- 
deed throughout, has been suffered to remain as 
a sketch, it should be remembered that all 
theory can in strictness only point out leading 
principles, under the guidance of which, . prac- 
tice may proceed with vigour and be enabled to 
attain legitimate results. 



Digitized by 



Google 



PART I. 

PHYSIOLOGICAL COLOURS. 



I. 

We naturally place these colours first, because 
they belong altogether^ or in a great degreci to 
the subject* — to the eye itself. They are the 
foundation of the whole doctrine, and open to 
our view the chromatic harmony on which so 
much difference of opinion has existed. They 
have been hitherto looked upon as extrinsic and 
casual, as illusion and infirmity : their appear- 
ances have been known from ancient date ; but, 
as they were too evanescent to be arrested, they 
were banished into the region of phantoms, and 
under this idea have been very variously described. 



Thus they are called colores adventicii by Boyle ; 
imaginarii and phantastici by Rizetti ; by Buffon, 
cotUeurs accidentelles ; by Scherfer, schein/arben 
(apparent colours) ; ocular illusions and deceptions 

* The German distlDCtion between subject and object is so 
generally understood and adopted, that it is hardly necessary 
to explain that the subject is the individual, in this case the 
beholder ; the object, cdl thai is wit/umt him, — I. 



Digitized by 



Google 



2 PHYSIOLOGICAL COLOURS. 

of sight by many ; by Hamberger, vitia fugitiva ; 
by Darwin, octilar spectra. 

3. 

We have called them physiological because 
they belong to the eye in a healthy state ; be- 
cause we consider them as the necessary con- 
ditions of vision ; the lively alternating action of 
which, with reference to external objects and a 
principle within it, is thus plainly indicated. 

4. 

To these we subjoin the pathological colours, 
which, like all deviations from a constant law, 
aflford a more complete insight into the nature of 
the physiological colours. 

EFFECTS OF LIGHT AND DARKNESS ON THE EYE. 
5. 

The retina, after being acted upon by light or 
darkness, is found to be in two different states, 
which are entirely opposed to each other. 

6. 

If we keep the eyes open in a totally dark 
place, a certain sense of privation is experienced. 
The organ is abandoned to itself; it retires into 
itself. That stimulating and grateful contact is 
wanting by means of which it is connected with 
the external world, and becomes part of a whole. 



Digitized by 



Google 



EFFECTS OF LIGHT AND DARKNESS. 3 

7. 

If we look on a white, strongly illumined sur- 
face, the eye is dazzled, and for a time is in- 
capable of distinguishing objects moderately 
lighted. 

8. 

The whole of the retina is acted on in each of 
these extreme states, and thus we can only ex- 
perience one of these effects at a time. In the 
one case (6) we found the organ in the utmost 
relaxation and susceptibility; in the other (7) 
in an overstrained state, and scarcely susceptible 
at all. 

9. 

If we pass suddenly from the one state to the 
other, even without supposing these to be the 
extremes, but only, perhaps, a change from 
bright to dusky, the difference is remarkable, 
and we find that the effects last for some time. 

10. 

In passing fix>m bright daylight to a dusky 
place we distinguish nothing at first : by degrees 
the eye recovers its susceptibility ; strong eyes 
sooner than weak ones ; the former in a minute, 
while the latter may require seven or eight 
minutes. 

11. 

The fact that the eye is not susceptible to faint 

b2 



Digitized by 



Google 



4 EFFECTS OF LIGHT AND DARKNESS 

impressions of light, if we pass from light to 
comparative darkness, has led to curious mis- 
takes in scientific observations. Thus an ob- 
server, whose eyes required some time to recover 
their tone, was long under the impression that 
rotten wood did not emit light at noon-day, even 
in a dark room. The fact was, he did not see the 
faint light, because he was in the habit of pass- 
ing from bright sunshine to the dark room, and 
only subsequently remained so long there that 
the eye had time to recover itself 

The same may have happened to Doctor 
Wall, who, in the daytime, even in a dark room, 
could hardly perceive the electric light of amber. 

Our not seeing the stars by day, as well as the 
improved appearance of pictures seen through a 
double tube, is also to be attributed to the same 
cause. 

12. 

If we pass from a totally dark place to one 
illumined by the sun, we are dazzled. In coming 
from a lesser degree of darkness to light that is 
not dazzling, we perceive all objects clearer and 
better : hence eyes that have been in a state of 
repose are in all cases better able to perceive 
moderately distinct appearances. 

Prisoners who have been long confined in 
darkness acquire so great a susceptibility of the 
retina, that even in the dark (probably a dark- 



Digitized by 



Google 



ON THE EYE- O 

ness very slightly illumined) they can still dis- 
tinguish objects. 

13. 

In the act which we call seeing, the retina is 
at one and the same time in different and even 
opposite states. The greatest brightness, short 
of dazzling, acts near the greatest darkness. In 
this state we at once perceive all the intermediate 
gradations of chiaroscuro^ and all the varieties of 
hues. 

14. 

We will proceed in due order to consider and 
examine these elements of the visible world, as 
well as the relation in which the organ itself 
stands to them, and for this purpose we take the 
simplest objects. 



IL 



EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE. 

15. 

In the same manner as the retina generally is 
affected by brightness and darkness, so it is 
affected by single bright or dark objects. If 
light and dark produce different results on the 
whole retina, so black and white objects seen at 



Digitized by 



Google 



6 EFFECTS OF BLACK AND 

the same time produce the same states together 
which light and dark occasioned in succession. 

16. 

A dark object appears smaller than a bright 
one of the same size. Let a white disk be placed 
on a black ground, and a black disk on a white 
ground, both being exactly similar in size ; let 
them be seen together at some distance, and we 
shall pronounce the last to be about a fifth part 
smaller than the other. If the black circle be 
made larger by so much, they will appear equal.* 

17. 

Thus Tycho de Brahe remarked that the moon 
in conjunction (the darker state) appears about 
a fifth part smaller than when in opposition (the 
bright full state). The first crescent appears to 
belong to a larger disk than the remaining dark 
portion, which can sometimes be distinguished 
at the period of the new moon. Black dresses 
make people appear smaller than light ones. 
Lights seen behind an edge make an apparent 
notch in it. A ruler, behind which the flame of 
a light just appears, seems to us indented. The 
rising or setting sun appears to make a notch in 
the horizon. 

18. 
Black, as the equivalent of darkness, leaves 

* Plate i. fig. 1. 



Digitized by 



Google 



Full 



Digitized by 



Google 



Digitized by 



Google 



WHITE OBJECTS ON THE EYE. 7 

the organ in a state of repose -, white^ as the re- 
presentative of light, excites it. We may, per- 
haps, conclude from the above experiment (16) 
that the unexcited retina, if left to itself, is drawn 
together, and occupies a less space than in its 
active state, produced by the excitement of light. 
Hence Kepler says very beautifully : '* Certum 
est vel in retind caussd picturae, vel in spiritibus 
caussft impressionis, exsistere dilatationem luci- 
dorum.*' — Paralip. in Vitellionem^ p. 220. Scher- 
fer expresses a similar conjecture. — Note A. 

19. 

However this may be, both impressions 
derived from such objects remain in the organ 
itself, and last for some time, even when the 
external cause is removed. In ordinary ex- 
perience we scarcely notice this, for objects 
are seldom presented to us which are very 
strongly relieved from each other, and we avoid 
looking at those appearances that dazzle the 
sight In glancing from one object to another; 
the succession of images appears to us distinct ; 
we are not aware that some portion of the im- 
pression derived from the object first contem- 
plated passes to that which is next looked at. 

20. 

If in the morning, on waking, when the eye 
is very susceptible, we look intently at the bars 



Digitized by 



Google 



8 EFFECTS OF BLACK AND 

of a window relieved against the dawning sky, 
and then shut our eyes or look towards a totally 
dark place, we shall see a dark cross on a light 
ground before us for some time. 

21. 

Every image occupies a certain space on the 
retina, and of course a greater or less space in 
proportipn as the object is seen near or at a 
distance. If we shut the eyes immediately 
after looking at the sun we shall be surprised to 
find how small the image it leaves appears. 

22. 

If, on the other hand, we turn the open eye 
towards the side of a room, and consider the 
visionary image in relation to other objects, we 
shall always see it larger in proportion to the 
distance of the surface on which it is thrown. 
This is easily explained by the laws of perspec- 
tive, according to which a small object near 
covers a great one at a distance. 

23. 

The duration of these visionary impressions 
varies with the powers or structure of the eye 
in different individuals, just as the time neces- 
sary for the recovery of the tone of the retina 
varies in passing from brightness to darkness 
(10) : it can be measured by minutes and se- 



Digitized by 



Google 



WHITE OBJECTS ON THE EYE. 9 

condsy indeed much more exactly than it could 
formerly have been by causing a lighted lin- 
stock to revolve rapidly, so as to appear a cir- 
cle, — Note B. 

24. 

But the force with which an impinging light 
impresses the eye is especially worthy of atten- 
tion. The image of the sun lasts longest ; other 
objects, of various degrees of brightness, leave 
the traces of their appearance on the eye for a 
proportionate time. 

25. 

These images disappear by degrees, and 
diminish at once in distinctness and in size. 

26. 

They are reduced from the contour inwards, 
and the impression on some persons has been 
that in square images the angles become gra- 
dually blunted till at last a diminished round 
image floats before the eye. 

27. 

Such an image, when its impression is no 
more observable, can, immediately after, be 
again revived on the retina by opening and 
shutting the eye, thus alternately exciting and 
resting it. 



Digitized by 



Google 



10 EFFECTS OF BLACK AND 

28. 

Images may remain on the retina in morbid 
affections of the eye for fourteen, seventeen 
minutes, or even longer. This indicates extreme 
weakness of the organ, its inability to recover 
itself; while visions of persons or things which 
are the objects of love or aversion indicate the 
connexion between sense and thought. 

29. 
If, while the image of the window-bars before 
mentioned lasts, we look upon a light grey sur- 
face, the cross will then appear light and the 
panes dark. In the first case (20) the image 
was like the original picture, so that the vision- 
ary impression also could continue unchanged ; 
but in the present instance our attention is 
excited by a contrary effect being produced. 
Various examples have been given by observers 
of nature. 

30. 

The scientific men who made observations in 
the Cordilleras saw a bright appearance round 
the shadows of their heads on some clouds. 
This example is a case in point ; for, while they 
fixed their eyes on the dark shadow, and at the 
same time moved from the spot, the compensa- 
tory light image appeared to float round the 



Digitized by 



Google 



WHITE OBJECTS ON THE EYE. 1 1 

real dark one. If we look at a black disk on a 
light grey surface, we shall presently, by 
changing the direction of the eyes in the slight- 
est degree, see a bright halo floating round the 
dark circle. 

A similar circumstance happened to myself: 
for while, as I sat in the open air, I was talking 
to a man who stood at a little distance from me 
relieved on a grey sky, it appeared to me, as I 
slightly altered the direction of my eyes, after 
having for some time looked fixedly at him, 
that his head was encircled with a dazzling 
light. 

In the same way probably might be explained 
the circumstance that persons crossing dewy 
meadows at sunrise see a brightness round each 
other's heads ;* the brightness in this case may 
be also iridescent, as the phenomena ^of refrac- 
tion come into the account. 

Thus again it has been asserted that the 
shadows of a balloon thrown on clouds were 
bordered with bright and somewhat variegated 
circles. 

Beccaria made use of a paper kite in some 
experiments on electricity. Round this kite 
appeared a small shining cloud varying in size ; 
the same brightness was even .observed round 
part of the string. Sometimes it disappeared, 

* See the Life of Benvenuto Cellini, vol. i. p. 453. [ Milan edi- 
tion, 1806.— T. 



Digitized by 



Google 



12 EFFECTS OF BLACK AND 

and if the kite moyed faster the light appeared 
to float to and fro for a few moments on the 
place before occupied. This appearance, which 
could not be explained by those who observed 
it at the time, was the image which the eye re- 
tained of the kite relieved as a dark mass on 
a bright sky ; that image being changed into a 
light mass on a comparatively dark back- 
ground. 

In optical and especially in chromatic expe- 
riments, where the observer has to do with 
bright lights whether colourless or coloured, 
great care should be taken that the spectrum 
which the eye retains in consequence of a pre- 
vious observation does not mix with the suc- 
ceeding one, and thus afiect the distinctness 
and purity of the impression. 

31. 

These appearances have been explained as 
follows : That portion of the retina on which 
the dark cross (29) was impressed is to be con- 
sidered in a state of repose and susceptibility. 
On this portion therefore the moderately light 
surface acted in a more lively manner than on 
the rest of the retina, which had just been im- 
pressed with the light through the panes, and 
which, having thus been excited by a much 
stronger brightness, could only view the grey 
surface as a dark. 



Digitized by 



Google 



WHITE OBJECTS ON THE EYE. 13 

32. 

This mode of explanation appears sufficient 
for the cases in question, but, in the considera- 
tion of phenomena hereafter to be adduced, we 
are forced to trace the effects to higher sources. 

33. 
The eye after sleep exhibits its vital elas- 
ticity more especially by its tendency to al- 
ternate its impressions, which in the simplest 
form change from dark to light, and from light 
to dark. The eye cannot for a moment remain 
in a particular state determined by the object it 
looks upon. On the contrary, it is forced to a 
sort of opposition, which, in contrasting extreme 
with extreme, intermediate degree with inter- 
mediate degree^ at the same time combines these 
opposite impressions, and thus ever tends to a 
whole, whether the impressions are successive, 
or simultaneous and confined to one image. 

34. 

Perhaps the peculiarly grateful sensation 
which we experience in looking at the skilfully 
treated chiaro-scuro of colourless pictures and 
similar works of art arises chiefly from the 
simultaneous impression of a whole, which by the 
organ itself is sought, rather than arrived at, in 
succession^ and which, whatever may be the re- 
sult, can never be arrested. 



Digitized by 



Google 



14 GREY SURFACES AND OBJECTS. 



III. 

GREY SURFACES AND OBJECTS. 
35. 

A MODERATE light is esscDtial to many chro- 
matic experiments. This can be presently ob- 
tained by surfaces more or less grey, and thus 
we have at once to make ourselves acquainted 
with this simplest kind of middle tint, with re- 
gard to which it is hardly necessary to observe, 
that in many cases a white surface in shadow, 
or in a low light, may be considered equivalent 
to a grey. 

36. 

Since a grey surface is intermediate between 
brightness and darkness, it admits of our illus- 
trating a phenomenon before described (29) by 
an easy experiment. 

37. 

Let a black object be held before a grey sur- 
face, and let the spectator, after looking stead- 
fastly at it, keep his eyes unmoved while it is 
taken away : the space it occupied appears 
much lighter. Let a white object be held up in 
the same manner : on taking it away the space 
it occupied will appear much darker than the 



Digitized by 



Google 



GREY SURFACES AND OBJECTS. 15 

rest of the surface. Let the spectator in both 
cases turn his eyes this way and that on the sur- 
face, the Tisionary images will move in like 
manner. 

38. 

A grey object on a black ground appears 
much brighter than the same object on a white 
ground. If both comparisons are seen together 
the spectator can hardly persuade himself that 
the two greys are identical. We believe this 
again to be a proof of the great excitability of 
the retina, and of the silent resistance which 
every vital principle is forced to exhibit when 
any definite or immutable state is presented to 
it. Thus inspiration already presupposes ex- 
piration ; thus every systole its diastole. It is 
the universal formula of life which manifests 
itself in this as in all other cases. When dark- 
ness is presented to the eye it demands bright- 
ness, and vice versd : it shows its vital energy, 
its fitness to receive the impression of the object, 
precisely by spontaneously tending to an op- 
posite state. 



Digitized by 



Google 



16 DAZZLING COLOURLESS OBJECTS. 

IV. 

DAZZLING COLOURLESS OBJECTS. 
39. 

If we look at a dazzling, altogether colourless 
object, it makes a strong lasting impression, and 
its after- vision is accompanied by an appearance 
of colour. 

40. 

Let a room be made as dark as possible ; let 
there be a circular opening in the window- 
shutter about three inches in diameter, which 
may be closed or not at pleasure. The sun 
being suffered to shine through this on a white 
surface, let the spectator from some little dis- 
tance fix his eyes on the bright circle thus 
admitted. The hole being then closed, let him 
look towards the darkest part of the room ; a 
circular image will now be seen to float before 
him. The middle of this circle will appear 
bright, colourless, or somewhat yellow, but the 
border will at the same moment appear red. 

After a time this red, increasing towards the 
centre, covers the whole circle, and at last the 
bright central point No sooner, however, is 
the whole circle red than the edge begins to be 
blue, and the blue gradually encroaches inwards 



Digitized by 



Google 



DAZZLING COLOURLESS OBJECTS. 17 

on the red. When the whole is blue the edge 
becomes dark and colourless. This darker edge 
again slowly encroaches on the blue till the 
whole circle appears colourless. The image 
then becomes gradually fainter, and at the same 
time diminishes in size. Here again we see 
how the retina recovers itself by a succession of 
vibrations after the powerful external impression 
it received. (25,26.) 

41. 

By several repetitions similar in result, I found 
the comparative duration of these appearances 
in my own case to be as follows : — 

I looked on the bright circle five seconds, and 
then, having closed the aperture, saw the co- 
loured visionary circle floating before me. After 
thirteen seconds it was altogether red ; twenty- 
nine seconds next elapsed till the whole was blue, 
and forty-eight seconds till it appeared colour- 
less. By shutting and opening the eye I con- 
stantly revived the image, so that it did not 
quite disappear till seven minutes had elapsed. 

Future observers may find these periods 
shorter or longer as their eyes may be stronger 
or weaker (23), but it would be very remarkable 
if, notwithstanding such variations, a correspond- 
ing proportion as to relative duration should be 
found to exist. 



Digitized by 



Google 



18 DAZZLING COLOURLESS OBJECTS. 

42. 

But this remarkable phenomenon no sooner 
excites our attention than we observe a new 
modification of it. 

If we receive the impression of the bright 
circle as before, and then look on a light grey 
surface in a moderately lighted room, an image 
again floats before us; but in this instance a 
dark one : by degrees it is encircled by a green 
border that gradually spreads Inwards over the 
whole circle, as the red did in the former 
instance. As soon as this has taken place a 
dingy yellow appears, and, filling the space as 
the blue did before, is finally lost in a negative 
shade. 

43. 

These two experiments may be combined by 
placing a black and a white plane surface next 
each other in a moderately lighted room, and 
then looking alternately on one and the other 
as long as the impression of the light cirple lasts: 
the spectator will then perceive at first a red 
and green image alternately, and afterwards the 
other changes. After a little practice the two 
opposite colours may be perceived at once, by 
causing the floating image to fall on the junction 
of the two planes. This can be more conv^- 
niently done if the planes are at some distance^ 
for the spectrum then appears larger. 



Digitized by 



Google 



DAZZLING COLOURLESS OBJECTS. 19 

44. 

I happened to be in a forge towards evening 
at the moment when a glowing mass of iron was 
placed on the anvil ; I had fixed my eyes stead- 
fastly on it, and, turning round, I looked acci- 
dentally into an open coal- shed: a large red 
image now floated before my eyes, and, as I 
turned them from the dark opening to the light 
boards of which the shed was constructed, the 
image appeared half green, half red, according 
as it had a lighter or darker ground behind it. 
I did not at that time take notice of the sub- 
sequent changes of this appearance. 

45. 

The after- vision occasioned by a total dazzling 
of the retina corresponds with that of a circum- 
scribed bright object. The red colour seen by 
persons who are dazzled with snow belongs to 
this class of phenomena, as well as the singularly 
beautiful green colour which dark objects seem 
to wear after looking long on white paper in the 
sun. The details of such experiments may be 
investigated hereafter by those whose young 
eyes are capable of enduring such trials further 
for the sake of science. 

46. 
With these examples we may also class the 
black letters which in the evening light appear 

c 2 



Digitized by 



Google 



20 COLOURED OBJECTS. 

red. Perhaps we might insert under the same 
category the story that drops of blood appeared 
on the table at which Henry IV. of France had 
seated himself with the Due de Guise to play at 
dice. 



V. 

COLOURED OBJECTS. 
47. 

We have hitherto seen the physiological 
colours displayed in the after- vision of colour- 
less bright objects, and also in the after-vision 
of general colourless brightness ; we shall now 
find analogous appearances if a given colour be 
presented to the eye: in considering this, all 
that has been hitherto detailed must be present 
to bur recollection. 

48. 

The impression of coloured objects remains 
in the eye like that of colourless ones, but in 
this case the energy of the retina, stimulated as 
it is to produce the opposite colour, will be more 
apparent. 

49. 

Let a small piece of bright-coloured paper or 
silk stuff be held before a moderately lighted 
white surface ; let the observer look steadfastly 



Digitized by 



Google 



COLOURED OBJECTS. 2 1 

on the small coloured object, and let it be taken 
away after a time while his eyes remain un- 
moved ; the spectrum of another colour will then 
be visible ^on the white plane. The coloured 
paper may be also left in its place while the eye 
is directed to another part of the white plane ; 
the same spectrum will be visible there too, for 
it arises from an image which now belongs to 
the- eye. 

50. 

In order at once to see what colour will be 
evoked by this contrast, the chromatic circle * 
may be referred to. The colours are here ar- 
ranged in a general way according to the 
natural order, and the arrangement will be 
found to be directly applicable in the present 
case ; for the colours diametrically opposed to 
each other in this diagram are those which reci* 
procally evoke each other in the eye. Thus, 
yellow demands purple ; orange, blue ; red, 
green ; and vice versd : thus again all interme- 
diate gradations reciprocally evoke each other ; 
the simpler colour demanding the compound, 
and vice versd. — Note C. 

51. 

The cases here under consideration occur 
oftener than we are aware in ordinary life ; in- 

* Plate l,fig. 3. 



Digitized by 



Google 



22 COLOURED OBJECTS. 

deed, an attentive observer sees these appear- 
ances everywhere, while, on the other hand, the 
un instructed, like our predecessors, consider 
them as temporary visual defects, sometimes 
even as symptoms of disorders in the eye, thus 
exciting serious apprehensions. A few remark- 
able instances may here be inserted. 

52. 

I had entered an inn towards evening, and, 
as a well-favoured girl, with a brilliantly fair 
complexion, black hair, and a scarlet bodice, 
came into the room, I looked attentively at her 
as she stood before me at some distance in half 
shadow. As she presently afterwards turned 
away, I saw on the white wall, which was now 
before me, a black face surrounded with a bright 
light, while the dress of the perfectly distinct 
figure appeared of a beautiful sea-green. 

53. 

Among the materials for optical experiments, 
there are portraits with colours and shadows 
exactly opposite to the appearance of nature. 
The spectator, after having looked at one of 
these for a time, will see the visionary figure 
tolerably true to nature. This is conformable 
to the same principles, and consistent with ex- 
perience, for, in the former instance, a negress 
with a white head-dress would have given me a 
white face surrounded with black. In the case 



Digitized by 



Google 



COLOURED OBJECTS. 23 

of the painted figures, however, which are com- 
monly small, the parts are not distinguishable 
by every one in the after-image. 

54. 

A phenomenon which has before excited 
attention among the observers of nature is to 
be attributed, I am persuaded, to the same 
cause. 

It has been stated that certain flowers, towards 
evening in summer, coruscate, become phos- 
phorescent, or emit a momentary light Some 
persons have described their observation of 
this minutely. I had often endeavoured to 
witness it myself, and had even resorted to 
artificial contrivances to produce it. 

On the 19th of June, 1799, late in the evening, 
when the twilight was deepening into a clear 
night, as I was walking up and down the garden 
with a friend, we very distinctly observed a 
flame-like appearance near the oriental poppy, 
the flowers of which are remarkable for their 
powerful red colour. We approached the place 
and looked attentively at the flowers, but could 
perceive nothing further, till at last, by passing 
and repassing repeatedly, while we looked side- 
ways on them, we succeeded in renewing the 
appearance as often as we pleased. It proved 
to be a physiological phenomenon, such as 
others we have described, and the apparent 



Digitized by 



Google 



24 COLOURED OBJECTS. 

coruscation was notbiug but the spectrum of the 
flower in the compensatory blue-green colour. 

In looking directly at a flower the image is 
not produced, but it appears immediately as the 
direction of the eye is altered. Again, by look- 
ing sideways on the object, a double image is 
seen for a moment, for the spectrum then; 
appears near and on the real object. 

The twilight accounts for the eye being in a 
perfect state of repose, and thus very susceptible, 
and the colour of the poppy is sufficiently 
powerful in the summer twilight of the longest 
days to act with full effect and produce a com- 
pensatory image. I have no doubt these ap- 
pearances might be reduced to experiment, and 
the same effect produced by pieces of coloured 
paper. Those who wish to take the most 
effectual means for observing the appearance in 
nature — suppose in a garden — should fix the eyes 
on the bright flowers selected for the purpose, 
and, immediately after, look on the gravel path. 
This will be seen studded with spots of the 
opposite colour. The experiment is practicable 
on a cloudy day, and even in the brightest sun- 
shine, for the sun-light, by enhancing the bril- 
liancy of the flower, renders it fit to produce the 
compensatory colour sufficiently distinct to be 
perceptible even in a bright light. Thus, peonies 
produce beautiful green, marigolds vivid blue 
spectra. 



Digitized by 



Google 



COLOURED OBJECTS, 25 

55. 

As the opposite colour is produced by a con- 
stant law in experiments with coloured objects 
on portions of the retina, so the same effect 
takes place when the whole retina is impressed 
with a single colour. We may convince our- 
selves of this by means of coloured glasses. If 
we look long through a blue pane of glass, 
everything will afterwards appear in sunshine to 
the naked eye, even if the sky is grey and the 
scene colourless. In like manner, in taking off 
green spectacles, we see all objects in a red 
light. Every decided colour does a certain vio- 
lence to the eye, and forces the organ to 
opposition. 

56. 

We have hitherto seen the opposite colours 
producing each other successively on the retina : 
it now remains to show by experiment that the 
same effects can exist simultaneously. If a 
coloured object impinges on one part of the 
retina, the remaining portion at the same mo- 
ment has a tendency to produce the compensa- 
tory colour. To pursue a former experiment, if 
we look on a yellow piece of paper placed on a 
white surface, the remaining part of the organ 
has already a tendency to produce a purple hue 
on the colourless surface : in this case the small 
portion of yellow is not powerful enough to pro- 



Digitized by 



Google 



26 COLOURED OBJECTS. 

duce this appearance distinctly, but, if a white 
paper is placed on a yellow wall, we shall see 
the white tinged with a purple hue. 

57. 

Although this experiment may be made with 
any colours, yet red and green are particularly 
recommended for it, because these colours seem 
powerfully to evoke each other. Numerous in- 
stances occur in daily experience. If a green 
paper is seen through striped or flowered muslin, 
the stripes or flowers will appear reddish. A 
grey building seen through green pallisades 
appears in like manner reddish. A modification 
of this tint in the agitated sea is also a com- 
pensatory colour : the light side of the waves 
appears green in its own colour, and the sha- 
. dowed side is tinged with the opposite hue. The 
different direction of the waves with reference 
to the eye produces the same effect. Objects 
seen through an opening in a red or green cur- 
tain appear to wear the opposite hue. These 
appearances will present themselves to the atten- 
tive observer on all occasions, even to an un- 
pleasant degree. 

58. 

Having made ourselves acquainted with the 
simultaneous exhibition of these effects in direct 
cases, we shall find that we can also observe 
them by indirect means. If we place a piece of 



Digitized by 



Google 



COLOURED OBJECTS. 27 

paper of a bright orange colour on the white 
surface, we shall, after looking intently at it, 
scarcely perceive the compensatory colour on 
the rest of the surface : but when we take the 
orange paper away, and when the blue spectrum 
appears in its place, immediately as this spec- 
trum becomes fully apparent, the rest of the 
surface will be overspread, as if by a flash, with 
a reddish-yellow light, thus exhibiting to the 
spectator in a lively manner the productive 
energy of the organ, in constant conformity with 
the same law. 

59. 

As the compensatory colours easily appear, 
where they do not exist in nature, near and 
after the original opposite ones, so they are ren- 
dered more intense where they happen to mix 
with a similar real hue. In a court which was 
paved with grey limestone flags, between which 
grass had grown, the grass appeared of an ex- 
tremely beautiful green when the evening clouds 
threw a scarcely perceptible reddish light on 
the pavement. In an opposite case we find, 
in walking through meadows, where we see 
scarcely anything but green, the stems of trees 
and the roads often gleam with a reddish hue. 
This tone is not uncommon in the works of 
landscape painters, especially those who prac- 
tice in water-colours : they probably see it in 



Digitized by 



Google 



28 COLOURED OBJECTS. 

nature, and thus, unconsciously imitating it, 
their colouring is criticised as unnatural. 

60. 

These phenomena are of the greatest import- 
ance, since they direct our attention to the laws 
of visiod, and are a necessary preparation for 
future observations on colours. They show that 
the eye especially demands completeness, and 
seeks to eke out^the colorific circle in itself. 
The purple or violet colour suggested by yellow 
contains red and blue ; orange, which responds 
to blue, is composed of yellow and red ; green, 
uniting blue and yellow, demands red ; and so 
through all gradations of the most complicated 
combinations. That we are compelled in this 
case to assume three leading colours has been 
already remarked by other observers. 

61. 

When in this completeness the elements of 
which it is composed are still appreciable by 
the eye, the result is justly called harmony. 
We shall subsequently endeavour to show how 
the theory of the harmony of colours may be 
deduced from these phenomena, and how, sim- 
ply through these qualities, colours may be ca- 
pable of being applied to aesthetic purposes. 
This will be shown when we have gone through 
the whole circle of our observations, returning 
to the point from which we started. 



Digitized by 



Google 



COLOURED SHADOWS. 29 



VI. 



COLOURED SHADOWS. 
62. 

Before, however, we proceed further, we have 
yet to observe some very remarkable cases of 
the vivacity with which the suggested colours 
appear in the neighbourhood of others : we al- 
lude to coloured shadows. To arrive at these 
we first turn our attention to shadows that are 
colourless or negative. 

63. 

A shadow cast by the sun, in its full bright- 
ness, on a white surface, gives us no impression 
of colour ; it appears black, or, if a contrary 
light (here assumed to diflfer only in degree) can 
act upon it, it is only weaker, half-lighted, grey. 

64. 

Two conditions are necessary for the existence 
of coloured shadows : first, that the principal 
light tinge the white surface with some hue; 
secondly, that a contrary light illumine to a 
certain extent the cast shadow. 

66. 

Let a short, lighted candle be placed at twi- 
light on a sheet of white paper. Between it 
and the declining daylight let a pencil be placed 



Digitized by 



Google 



30 COLOURED SHADOWS. 

upright, SO that its shadow thrown by the candle 
may be lighted, but not overcome, by the weak 
daylight : the shadow will appear of the most 
beautiful blue. 

66. 

That this shadow is blue is immediately evi- 
dent; but we can only persuade ourselves by 
some attention that the white paper acts as a 
reddish yellow, by means of which the comple- 
mental blue is excited in the eye. — Note D. 

67. 

In all coloured shadows, therefore, we must 
presuppose a colour excited or suggested by the 
hue of the surface on which the shadow is 
thrown. This may be easily found to be the 
case by attentive consideration, but we may 
convince ourselves at once by the following ex- 
periment. 

68. 

Place two candles at night opposite each 
other on a white surface; hold a thin rod be- 
tween them upright, so that two shadows be 
cast by it; take a coloured glass and hold it be- 
fore one of the lights, so that the white paper 
appear coloured ; at the same moment the sha- 
dow cast by the coloured light and slightly illu- 
mined by the colourless one will exhibit the 
complemental hue. 



Digitized by 



Google 



COLOURED SHADOWS. 31 

69. 

An important consideration suggests itself 
here, to which we shall frequently have occasion 
to return. Colour itself is a degree of darkness 
(<rxi«poy) ; hence Kircher is perfectly right in 
calling it lumen opacatum. As it is allied to 
shadow, so it combines readily with it ; it ap* 
pears to us readily in and by means of shadow 
the moment a suggesting cause presents itself. 
We could not refrain from adverting at once to 
a fact which we propose to trace and develop 
hereafter. — Note E. 

70. 

Select the moment in twilight when the light 
of the sky is still powerful enough to cast a sha- 
dow which cannot be entirely effaced by the 
light of a candle. The candle may be so placed 
that a double shadow shall be visible, one from 
the candle towards the daylight, and another 
from the daylight towards the candle. If the 
former is blue the latter will appear orange- 
yellow : this orange-yellow is in fact, however, 
only the yellow-red light of the candle diffused 
over the whole paper, and which becomes visible 
in shadow. 

71. 
This is best exemplified by the former expe- 
riment with two candles and coloured glasses. 



Digitized by 



Google 



32 COLOURED SHADOWS. 

The surprising readiness with which shadow as- 
sumes a colour will again invite our attention 
in the further consideration of reflections and 
elsewhere. 

72. 

Thus the phenomena of coloured shadows 
may be traced to their cause without difficulty. 
Henceforth let any one who sees an instance of 
the kind observe only with what hue the light 
surface on which they are thrown is tinged. 
Nay, the colour of the shadow maybe considered 
as a chromatoscope of the illumined surface, for 
the spectator may always assume the colour of 
the light to be the opposite of that of the sha* 
dow, and by an attentive examination may as- 
certain this to be the fact in every instance. 

73. 

These appearances have been a source of 
great perplexity to former observers: for, as 
they were remarked chiefly in the open air, 
where they commonly appeared blue» they were 
attributed to a certain inherent blue or blue co- 
louring quality in the air. The inquirer can, 
however, convince himself, by the experiment 
with the candle in a room, that no kind of blue 
light or reflection is necessary to produce the 
effect in question. The experiment may be 
made on a cloudy day with white curtains drawn 



Digitized by 



Google 



COLOURED SHADOWS. 33 

before the light, and in a room where no trace 
of blue exists, and the blue shadow will be only 
SO much the more beautiful. 

74. 

De Saussure, in the description of his ascent 
of Mont Blanc, says, " A second remark, which 
may not be uninteresting, relates to the colour 
of the shadows. These, notwithstanding the 
most attentive observation, we never found dark 
blue, although this had been frequently the case 
in the plain. On the contrary, in fifty-nine in- 
stances we saw them once yellowish, six times 
pale bluish, eighteen times colourless or black, 
and thirty-four times pale violet. Some natural 
philosophers suppose that these colours arise 
from accidental vapours diffused in the air, which 
communicate their own hues to the shadows ; 
not that the colours of the shadows are occa- 
sioned by the reflection of any given sky colour 
or interposition of any given air colour: the 
above observations seem to favour this opinion." 
The instances given by De Saussure may be 
now explained and classed with analogous ex- 
amples without difficulty. 

At a great elevation the sky was generally 
free firom vapours, the sun shone in full force on 
the snow, so that it appeared perfectly white to 
the eye : in this case they saw the shadows 
quite colourless. If the air was charged with a 

D 



Digitized by 



Google 



34 COLOURED SHADOWS. 

certain degree of vapour, in consequence of 
which the light snow would assume a yellowish 
tone, the shadows were violet*coloured, and this 
eflFect, it appears, occurred oftenest. They saw 
also bluish shadows, but this happened less fre- 
quently ; and that the blue and violet were pale 
was owing to the surrounding brightness, by 
which the strength of the shadows was miti- 
gated. Once only they saw the shadow yellow- 
ish : in this case, as we have already seen (70), 
the shadow is cast by a colourless light, and 
slightly illumined by a coloured one. 

75. 

In travelling over the Harz in winter, 1 hap- 
pened to descend from the Brocken towards 
evening ; the wide slopes extending above and 
below me, the heath, every insulated tree and 
projecting rock, and all masses of both, were 
covered with snow or hoar-frost. The sun was 
sinking towards the Oder ponds.^ During the 
day, owing to the yellowish hue of the snow, 
shadows tending to violet had already been ob- 
servable ; these might now be pronounced to be 
decidedly blue, as the illumined parts exhibited 
a yellow deepening to orange. 

But as the sun at last was about to set, and 
its rays, greatly mitigated by the thicker va- 

* Reservoirs in which water is collected from various small 
streams, to work the mines. — ^T. 



Digitized by 



Google 



COLOURED SHADOWS. 35 

poars, began to diffuse a most beautiful red 
colour over the whole scene around me, the 
shadow colour changed to a green, in lightness 
to be compared to a seu-gre^i, in beauty to the 
green of the emerald. The appearance became 
more and more vivid : one might have imagined 
oneself in a fairy world, for every object had 
clothed itself in the two vivid and so beautifully 
harmonising colours, till at last, as the sun went 
down, the magnificent spectacle was lost in a 
grey twilight, and by degrees in a clear moon- 
and-starlight night. 

76. 

One of the most beautiful instances of co- 
loured shadows may be observed during the 
full moon. The candle-light and moon-light 
may be contrived to be exactly equal in 
force; both shadows may be exhibited with 
equal strength and clearness, so that both co- 
lours balance each other perfectly. A white 
surface being placed opposite the full moon, 
and the candle being placed a little on one side 
at a due distance, an opaque body is held be- 
fore the white plane A double shadow will 
then be seen : that cast by the moon and illu- 
mined by the candle-light will be a powerful 
red-yellow ; and contrariwise, that cast by the 
candle and illumined by the moon will appear 
of the most beautiful blue. The shadow, com- 
posed of the union of the two shadows, where 

d2 



Digitized by 



Google 



36 COLOURED SHADOWS. 

they cross each other, is black. The yellow 
shadow (74) cannot perhaps be exhibited in a 
more striking manner. The immediate vicinity 
of the blue and the interposing black shadow 
make the appearance the more agreeable. It 
will even be found, if the eye dwells long on 
these colours, that they mutually evoke and 
enhance each other, the increasing red in the 
one still producing its contrast, viz. a kind of 
sea-green. 

77. 

We are here led to remark that in this, and 
in all cases, a moment or two may perhaps be 
necessary to produce the complemental colour- 
The retina must be first thoroughly impressed 
with the demanding hue before the responding 
one can be distinctly observable. 

78. 

When divers are under water, and the sun- 
light shines into the diving-bell, everything is 
seen in a red light (the cause of which will be 
explained hereafter), while the shadows appear 
green. The very same phenomenon which I 
observed on a high mountain (75) is presented 
to others in the depths of the sea, and thus Na- 
ture throughout is in harmony with herself. 

79. 
Some observations and experiments which 
equally illustrate what has been stated with re- 



Digitized by 



Google 



COLOURED SHADOWS. 37 

gard to coloured objects and coloured shadows 
may be here added. Let a white paper blind 
be fastened inside the window on a winter even- 
ing; in this blind let there be an opening, 
through which the snow of some neighbouring 
roof can be seen. Towards dusk let a candle be 
brought into the room ; the snow seen through 
the opening will then appear perfectly blue, be- 
cause the paper is tinged with warm yellow by 
the candle-light. The snow seen through the 
aperture is here equivalent to a shadow illu- 
mined by a contrary light (76) » and may also 
represent a grey disk on a coloured surface (56). 

80. 

Another very interesting experiment may 
conclude these examples. If we take a piece 
of green glass of some thickness, and hold it so 
that the window bars be reflected in it, they 
will appear double owing to the thickness of the 
glass. The image which is reflected from the 
under surface of the glass will be green ; the 
image which is reflected from the upper surface, 
and which should be colourless, will appear red. 

The experiment may be very satisfactorily 
made by pouring water into a vessel, the inner 
surface of which can act as a mirror ; for both 
reflections may first be seen colourless while the 
water is pure, and then by tinging it, they will 
exhibit two opposite hues. 



Digitized by 



Google 



38 FAINT LIGHTS. 



VII. 



FAINT LIGHTS, 
81. 

Light, in its full force, appears purely white, 
and it gives this impression also in its highest 
degree of dazzling splendour. Light, which is^ 
not so powerful, can also, under various condi- 
tions, remain colouriess. Several naturalists 
and mathematicians have endeavoured to mea- 
sure its degrees— ^Lambert, Bouguer, Rumfort 

82. 

Yet an appearance of colour presently mani- 
fests itself in fainter lights, for in their relation 
to absolute light they resemble the coloured 
spectra of dazzling objects (39). 

83. 
A light of any kind becomes weaker, either 
when its own force, from whatever cause, is di- 
minished, or when the eye is so circumstanced 
or placed, that it cannot be sufficiently im- 
pressed by the action of the light. Those ap" 
pearances which may be called objective, come 
under the head of physical colours. We will 
only advert here to the transition from white to 
r^d heat in glowing iron. We may also observe 



Digitized by 



Google 



FAINT LIGHTS. 39 

that the flames of lights at night appear redder 
in proportion to their distance from the eye, — 
NoteR 

84. 

Candle-light at night acts as yellow when seen 
near ; we can perceive this by the effect it pro- 
duces on other cidours. At night a pale yellow 
is hardly to be distinguished from white; blue 
approaches to green, and rose-colour to orange. 

85. 

Candle-light at twilight acts powerfiilly as a 
yellow light : this is best proved by the purple 
blue shadows whioh^ under these circumstances, 
are evoked by the eye. 

86. 

The retina may be so excited by a strong 
light that it cannot perceive fainter lights (11) : 
if it perceive these they appear coloured : hence 
candle-light by day appears reddish, thus re- 
sembling, in its relation to fuller light, the spec- 
trum of a dazzling object ; nay, if at night we 
look long and intently on the flame of a light, 
it appears to increase in redness. 

87. 

There are faint lights which, notwithstanding 
their moderate lustre, give an impression of a 



Digitized by 



Google 



40 FAINT LIGHTS. 

white, or, at the most, of a light yellow appear- 
ance on the retina ; such as the moon in its full 
splendour. Rotten wood has even a kind of 
bluish light. All this will hereafter be the 
subject of further remarks. 

88. 

If at night we place a light near a white or 
greyish wall so that the surface be illumined 
from this central point to some extent, we find, 
on observing the spreading light at some dis- 
tance, that the boundary of the illumined surface 
appears to be surrounded with a yellow circle, 
which on the outside tends to red-yellow. We 
thus observe that when light direct or reflected 
does not act in its full force, it gives an impres* 
sion of yellow, of reddish, and lastly even of red. 
Here we find the transition to halos which we 
are accustomed to see in some mode or other 
round luminous points. 



VIII. 

SUBJECTIVE HALOS. 
89. 

Halos may be divided into subjective and ob- 
jective. The latter will be considered under the 
physical colours; the first only belong here. 
These are distinguished from the objective 



Digitized by 



Google 



SUBJECTIVE HALOS. 41 

faalos by the circumstance of their vanishing 
when the point of light which produces them on 
the retina is covered. 

90. 

We have before noticed the impression of a 
luminous object on the retina, and seen that it 
appears larger : but the effect is not at an end 
here, it is not confined to the impression of the 
image; an expansive action also takes place, 
spreading from the centre. 

91. 

That a nimbus of this kind is produced round 
the luminous image in the eye may be best seen 
in a dark room, if we look towards a moderately 
large opening in the window-shutter. In this 
case the bright image is surrounded by a cir- 
cular misty light. I saw such a halo bounded 
by a yellow and yellow-red circle on opening 
my eyes at dawn, on an occasion when I passed 
several nights in a bed-carriage. 

92. 

Halos appear most vivid when the eye is sus- 
ceptible from having been in a state of repose. 
A dark background also heightens their ap- 
pearance. Both causes account for our seeing 
them so strong if a light is presented to the eyes 



h: UNIVCf^SITY -'' 

r OF ^i 



Xi^3^.? Jwj}^'^ Digitized by VjOOQ IC 



42 SUBJECTIVE HAL08. 

on waking at night. These conditions were 
combined when Descartes after sleeping, as he 
sat in a ship, remarked such a yiyidly^oloured 
halo round the light. 

93. 

A light must shine moderately, not dazzle, in 
order to produce the impression of a halo in the 
eye ; at all events the halos of dazzling lights 
cannot be observed. We see a splendour of 
this kind round the image of the sun reflected 
from the surface of water. 

94. 

A halo of this description, attentively observed, 
is found to be encircled towards its edge with a 
yellow border: but even here the expansive 
action, before alluded to^ is not at an end, but 
appears still to extend in varied circles. 

95. 

Several cases seem to indicate a circular ac- 
tion of the retina, whether owing to the round 
form of the eye itself and its different parts, or 
to some other cause. 

96. 

If the eye is pressed only in a slight degree 
from the inner corner, darker or lighter circles 



Digitized by 



Google 



SUBJECTIVE HALOS. 43 

appear. At night, even without pressure, we 
can sometimes perceive a succession of such 
circles emerging from, or spreading over, each 
other. 

97. 

We have already seen that a yellow border is 
apparent round the white space illumined by a 
light placed near it. This may be a kind of 
objective halo. (88.) 

98. 

Subjective halos may be considered as the 
result of a conflict between the light and a living 
surface. From the conflict between the excit- 
ing principle and the excited, an undulating 
motion arises, which may be illustrated by a 
comparison with the circles on water. The 
stone thrown in drives the water in all direc- 
tions ; the efiect attains a maximum, it reacts, 
and being opposed, continues under the surface. 
The efiect goes on, culminates again, and thus 
the circles are repeated. If we have ever re- 
marked the concentric rings which appear in a 
glass of water on trying to produce a tone by 
rubbing the edge ; if we call to mind the inter- 
mitting pulsations in the reverberations of bells, 
we shall approach a conception of what may 
take place on the retina when the image of a 
luminous object impinges on it, not to mention 



Digitized by 



Google 



44 SUBJECTIVE HALOS. 

that as a living and elastic structure, it has al- 
ready a circular principle in its organisation. — 
Note G. 

99. 

The bright circular space which appears 
round the shining object is yellow, ending in 
red: then follows a greenish circle, which is 
terminated by a red border. This appears to be 
the usual phenomenon where the luminous body 
is somewhat considerable in size. These halos 
become greater the more distant we are from 
the luminous object. 

100. 

Halos may, however, appear extremely small 
and numerous when the impinging image is 
minute, yet powerful, in its effect. The ex» 
periment is best made with a piece of gold-leaf 
placed on the ground and illumined by the sun. 
In these cases the halos appear in variegated 
rays. The iridescent appearance produced in 
the eye when the sun pierces through the leaves 
of trees seems also to belong to the same class 
of phenomena. 



Digitized by 



Google 



45 



PATHOLOGICAL COLOURS. 



APPENDIX. 
101. 

We are now sufficiently acquainted with the 
physiological colours to distinguish them from 
the pathological. We know what appearances 
belong to the eye in a healthy state, and are ne- 
cessary to enable the organ to exert its complete 
vitality and activity. 

102. 

Morbid phenomena indicate in like manner 
the existence of organic and physical laws : for 
if a living being deviates from those rules with 
reference to which it is constructed, it still seeks 
to agree with the general vitality of nature in 
conformity with general laws, and throughout its 
whole course still proves the constancy of those 
principles on which the universe has existed, 
and by which it is held together. 

103. 

We will here first advert to a very remarkable 
state in which the vision of many persons is 
found to be. As it presents a deviation from 
the ordinary mode of seeing colours, it might 
be fairly classed under morbid impressions ; but 
as it is consistent in itself, as it often occurs, 



Digitized by 



Google 



46 PATHOLOGICAL COLOURS. 

may extend to several members of a family, and 
probably does not admit of cure, we may con- 
sider it as bordering only on the nosological 
cases, and therefore place it first. 

104. 

I was acquainted with two individuals not 
more than twenty years of age, who were thus 
affected: both had bluish-grey eyes, an acute 
sight for near and distant objects, by day-light 
and candle-light, and their mode of seeing 
colours was in the main quite similar. 

105. 

They agreed with the rest of the world in 
denominating white, black, and grey in the usual 
manner. Both saw white untinged with any 
hue. One saw a somewhat brownish appear* 
ance in black, and in grey a somewhat reddish 
tinge. In general they appeared to have a very 
delicate perception of the gradations of light 
and dark. 

106. 

They appeared to see yellow, red-yellow, and 
yellow-red,* like others : in the last case they said 
they saw the yellow passing as it were over the 
red as if glazed : some thickly-ground carmine, 
which had dried in a saucer, they called red. 

* It has been found neceflsary to follow the author s nomencla- 
ture throughout. — T. 



Digitized by 



Google 



PATHOLOGICAL COLOURS. 47 



107. 



But now a striking difference presented itself. 
If the carmine was passed thinly over the white 
saucer, they would compare the light colour thus 
produced to the colour of the sky, and call it 
blue. If a rose was. shown them beside it, they 
would, in like manner, call it blue ; and in all the 
trials which were made, it appeared that they 
could not distinguish light blue from rose-colour. 
They confounded rose-colour, blue, and violet on 
all occasions: these colours only appeared to 
them to be distinguished from each other by de- 
licate shades of lighter, darker, intenser, or 
fainter appearance. 

108. 

Again they could not distinguish green from 
dark orange, nor, more especially, from a red 
brown. 

109. 

If any one, accidentally conversing with these 
individuals, happened to question them about 
surrounding objects, their answers occasioned 
the greatest perplexity, and the interrogator 
began to fancy his own wits were out of order. 
With some method we may, however, approach 
to a nearer knowledge of the law of this devia- 
tion from the general law. 



Digitized by 



Google 



48 PATHOLOGICAL COLOURS. 

110. 

These persons, as may be gathered from what 
has been stated, saw fewer colours than other 
people : hence arose the confusion of different 
colours. They called the sky rose-colour, and 
the rose blue, or vice versd. The question now 
is : did they see both blue or both rose-colour ? 
did they see green orange, or orange green ? 

Ill, 

This singular enigma appears to solve itself, 
if we assume that they saw no blue, but, instead 
of it, a light pure red, a rose-colour. We can 
comprehend what would be the result of this by 
means of the chromatic diagram. 

112. 

If we take away blue from the chromatic 
circle we shall miss violet and green as well. 
Pure red occupies the place of blue and violet, 
and in again mixing with yellow the red pro- 
duces orange where green should be. 

113. 

Professing to be satisfied with this mode of 
explanation, we have named this remarkable de- 
viation from ordinary vision " Acyanoblepsia." * 
We have prepared some coloured figures for 

♦ Non-perceptioii of blue. 



Digitized by 



Google 



PATHOLOGICAL COLOURS. 49 

its further elucidation^ and in explaining these 
we shall add some further details. Among the 
examples will be found a landscape, coloured in 
the mode in which the individuals alluded to 
appeared to see nature : the sky rose-colour, and 
all that should be green varying from yellow to 
brown red, nearly as foliage appears to us in 
autumn.* — Note H. 

114. 

We now proceed to speak of morbid and other 
extraordinary affections of the retina, by which 
the eye may be susceptible of an appearance of 
light without external light, reserving for a 
future occasion the consideration of galvanic 
light. 

115. 

If the eye receives a blow, sparks seem to 
spread from it. In some states of body, again, 
when the blood is heated, and the system much 
excited, if the eye is pressed first gently, and 
then more and more strongly, a dazzling and 
intolerable light may be excited. 

116. 

If those who have been recently couched ex- 
perience pain and heat in the eye, they fre- 

* It has not been thought necessary to copy the plates here 
referred to.— T. 



Digitized by 



Google 



50 PATHOLOGICAL COLOURS. 

quently see fiery flashes and sparks : these 
symptoms last sometimes for a week of fortnight, 
or till the pain and heat diminish. 

117. 

A person suflering from ear-ache saw sparks 
and balls of light in the eye during each attack, 
as long as the pain lasted. 

118. 

Persons suffering from worms often experience 
extraordinary appearances in the eye, sometimes 
sparks of fire, sometimes spectres of light, some- 
times frightful figures, which they cannot by an 
effort of the will cease to see : sometimes these 
appearances are double. 

119. 
Hypochondriacs frequently see dark objects, 
such as threads, hairs, spiders, flies, wasps. 
These appearances also exhibit themselves in 
the incipient hard cataract. Many see semi- 
transparent small tubes, forms like wings of 
insects, bubbles of water of various sizes, which 
fall slowly down, if the eye is raised: some^ 
times these congregate together so as to resem- 
ble the spawn of frogs ; sometimes they appear 
as complete spheres, sometimes in the form of 
lenses. 

120. 
As light appeared, in the former instances, 



Digitized by 



Google 



PATHOLOGICAL COLOURS. 51 

without external light, so also these images 
appear without corresponding external objects. 
The images are sometimes transient, sometimes 
they last during the patient's life. Colour, again, 
frequently accompanies these impressions: for 
hypochondriacs often see yellow-red stripes in 
the eye: these are generally more vivid and 
numerous in the morning, or when fEisting. 

121. 

We have before seen that the impression of 
any object may remain for a time in the eye : 
this we have found to be a physiological phe- 
nomenon (23) : the excessive duration of such 
an impression, on the other hand, may be con- 
sidered as morbid. 

122. 

The weaker the organ the longer the impres- 
sion of the image lasts. The retina does not so 
soon recover itself; and the effect may be con- 
sidered as a kind of paralysis (28). 

123. 
This is not to be wondered at in the case of 
dazzling lights. If any one looks at the sun, he 
may retain the image in his eyes for several 
days. Boyle relates an instance of ten years. 

124. 

The same takes place, in a certain degree, with 

e2 



Digitized by 



Google 



5*4 PATHOLOGICAL COLOURS. 

regard to objects that are not dazzling. Biisch 
relates of himself that the image of an engrav- 
ing, complete in all its parts, was impressed on 
his eye for seventeen minutes. 

125. 

A person inclined to fulness of blood retained 
the image of a bright red calico, with white spots, 
many minutes in the eye, and saw it float before 
everything like a veil. It only disappeared by 
rubbing the eye for some time. 

126. 

Scherfer observes that the red colour, which is 
the consequence of a powerful impression of 
light, may last for some hours. 

127. 

As we can produce an appearance of light on 
the retina by pressure on the eyeball, so by a 
gentle pressure a red colour appears^ thus cor- 
responding with the after-image of an impression 
of light. 

128. 

Many sick persons, on awaking, see every- 
thing in the colour of the morning sky, as if 
through a red veil : so, if in the evening they 
doze and wake again, the same appearance pre- 
sents itself. It remains for some minutes, and 



Digitized by 



Google 



PATHOLOGICAL COLOURS. 53 

always disappears if the eye is rubbed a little. 
Red stars and balls sometimes accompany the 
impression. This state may last for a consider- 
able time. 

129. 

The aeronauts, particularly Zambeccari and 
his companions, relate that they saw the moon 
blood-red at the highest elevation. As they had 
ascended above the vapours of the earth, through 
which we see the moon and sun naturally of such 
a colour, it may be suspected that this appear- 
ance may be classed with the pathological co- 
lours. The senses, namely, may be so influenced 
by an unusual state, that the whole nervous 
system, and particularly the retina, may sink 
into a kind of inertness and inexcitability. 
Hence it is not impossible that the moon might 
act as a very subdued light, and thus produce 
the impression of the red colour. The sun even 
appeared blood-red to the aeronauts of Ham- 
burgh. 

If those who are at some elevation in a balloon 
scarcely hear each other speak, may not this, 
too, be attributed to the inexcitable state of the 
nerves as well as to the thinness of the air? 

130. 

Objects are often seen by sick persons in 
variegated colours. Boyle relates an instance 



Digitized by 



Google 



54 PATHOLOGICAL COLOURS. 

of a lady, who, after a fall by which an eye wa& 
bruised, saw all objects, but especially white 
objects, glittering in colours, even to an intoler- 
able degree. 

131. 

Physicians give the name of " Chrupsia" to an 
affection of the sight, occurring in typhoid ma- 
ladies. In these cases the patients state that 
they see the boundaries of objects coloured where 
light and dark meet. A change probably takes 
place in the humours of the eye, through which 
their achromatism is affected. 

132. 

In cases of milky cataraot, a very turbid crys- 
talline lens causes the patient to see a red light. 
In a case of this kind, which was treated by the 
application of electricity, the red light changed 
by degrees to yellow, and at last to white, when 
the patient again began to distinguish objects. 
These changes of themselves warranted the con- 
clusion that the turbid state of the lens was gra- 
dually approaching the transparent state. We 
shall be enabled easily to trace this effect to its 
source as soon as we become better acquainted 
with the physical colours. 

133. 
If again it may be assumed that a jaundiced 



Digitized by 



Google 



PATHOLOGICAL COLOURS. 55 

patient sees through an actually yellow-coloured 
humour, we are at once referred to the depart- 
ment of chemical colours, and it is thus evident 
that we can only thoroughly investigate the 
chapter of pathological colours when we have 
made ourselves acquainted with the whole range 
of the remaining phenomena. What has been 
adduced may therefore suffice for the present, 
till we resume the further consideration of this 
portion of our subject 

134. 

In conclusion we may, however, at once ad- 
vert to some peculiar states or dispositions of 
the organ. 

There are painters who, instead of rendering 
the colours of nature, diffuse a general tone, a 
warm or cold hue, over the picture. In some, 
again, a predilection for certain colours displays 
itself; in others a want of feeling for harmony. 

135. 

Lastly, it is also worthy of remark, that sa- 
vage nations, uneducated people, and children 
have a great predilection for vivid colours ; that 
animals are excited to rage by certain colours ; 
that people of refinement avoid vivid colours iu 
their dress and the objects that are about them, 
and seem inclined to banish them altogether 
from their presence. — Note I 



Digitized by 



Google 



56 



PART 11. 

PHYSICAL COLOURS. 



136. 

We give this design ation to colours which are 
produced by certain material mediums : these 
mediums, however, have no colour themselves, 
and may be either transparent, semi-transpa- 
rent yet transmitting light, or altogether opaque. 
The colours in question are thus produced in 
the eye through such external given causes, or 
are merely reflected to the eye when by what- 
ever means they are already produced without 
us. Although we thus ascribe to them a certain 
objective character, their distinctive quality still 
consists in their being transient, and not to be 
arrested. 

137. 

They are called by former investigators co- 
lores apparentesy fluxi^ /ugitiviy phantasticiy falsiy 
variantes. They are also called speciosi and 
emphaticiy on account of their striking splen- 
dour. They are immediately connected with 
the physiological colours, and appear to have 
but little more reality : for, while in the produc- 



Digitized by 



Google 



PHYSICAL COLOURS. 57 

tioD of the physiological colours the eye itself 
was chiefly efficient, and we could only perceive 
the phenomena thus evoked within ourselves, 
but not without us, we have now to consider 
the fieu^t that colours are produced in the eye by 
means of colourless objects ; that we thus too 
have a colourless surface before us which is 
acted upon as the retina itself is, and that we 
can perceive the appearance produced upon it 
without us. In such a process, however, every 
observation will convince us that we have to do 
with colours in a progressive and mutable, but 
not in a final or complete^ state. 

138. 

Hence, in directing our attention to these 
physical colours, we find it quite possible to 
place an objective phenomenon beside a sub- 
jective one, and often by means of the union of 
the two successfully to penetrate farther into 
the nature of the appearance. 

139. 
Thus, in the observations by which we become 
acquainted with the physical colours, the eye is 
not to be considered as acting alone ; nor is the 
light ever to be considered in immediate relation 
with the eye : but we direct our attention espe- 
cially to the various effects produced by me- 
diums, those mediums being themselves colour- 
less. 



Digitized by 



Google 



58 PHYSICAL COLOURS. 

140. 

Light under these circumstances may be af- 
fected by three conditions. First, when it 
flashes back from the surface of a medium ; in 
considering which eatoptrical experiments invite 
our attention. Secondly, when it passes by the 
edge of a medium : the phenomena thus pro- 
duced were formerly called perioptieal ; we pre- 
fer the term paropticai. Thirdly, when it passes 
through either a merely light-transmitting or an 
actually transparent body ; thus constituting a 
class of appearances on which dioptrical expe- 
riments are founded. We have called a fourth 
class of physical colours epoptical, as the pheno- 
mena exhibit themselves on the colourless sur- 
face of bodies under various conditions, without 
previous or actual dye ()3a^iJ) . — Note K. 

141. 

In examining these categories with reference 
to our three leading divisions, according to 
which we consider the phenomena of colours 
in a physiological, physical, or chemical view, 
we find that the catoptrical colours are closely 
connected with the physiological ; the paropti- 
cai are already somewhat more distinct and 
independent ; the dioptrical exhibit themselves 
as entirely and strictly physical, and as having 
a decidedly objective character ; the epoptical, 
although still only apparent, may be considered 
as the transition to the chemical colours. 



Digitized by 



Google 



DIOPTRICAL COLOURS. 59 

142. 

If we were desirous of prosecuting our investi- 
gation strictly in the order of nature, we ought 
to proceed according to the classification which 
has just been made ; but in didactic treatises it 
is not of so much consequence to connect as to 
duly distinguish the various divisions of a sub- 
ject, in order that at last, when every single 
class and case has been presented to the mind, 
the whole may be embraced in one comprehen- 
sive view. We therefore turn our attention forth- 
with to the dioptrical class, in order at once to 
give the reader the full impression of the phy- 
sical colours, and to exhibit their characteristics 
the more strikingly. 



IX. 

DIOPTRICAL COLOURS. 
143. 

Colours are called dioptrical when a colour- 
less medium is necessary to produce them ; the 
medium must be such that light and darkness 
can act through it either on the eye or on oppo- 
site surfaces. It is thus required that the me- 
dium should be transparent, or at least capable, 
to a certain degree, of transmitting light. 



Digitized by 



Google 



60 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

144. 

According to these conditions we divide the 
dioptrical phenomena into two classes, placing 
in the first those which are produced by means 
of imperfectly transparent, yet light-transmit- 
ting mediums ; and in the second such as are 
exhibited when the medium is in the highest 
degree transparent. 



X- 

DIOPTRICAL COLOURS OF THE FIRST CLASS. 

145. 

Space, if we assume it to be empty, would 
have the quality of absolute transparency to 
our vision. If this space is filled so that the 
eye cannot perceive that it is so, there exists a 
more or less material transparent medium, 
which may be of the nature of air and gas, may 
be fluid or even solid. 

146. 

The pure and light-transmitting semi-trans- 
parent medium is only an accumulated form of 
the transparent medium. It may therefore be 
presented to us in three modes. 



Digitized by 



Google 



DIOPTRICAL COLOURS OP THE FIRST CLASS. 61 

147. 

The extreme degree of this accumulation is 
white ; the simplest, brightest, first, opaque 
occupation of space. 

148. 

Transparency itself, empirically considered, 
is already the first degree of the opposite state. 
The intermediate degrees from this point to 
opaque white are infinite. 

149. 

At whatever point short of opacity we arrest 
the thickening medium, it exhibits simple and 
remarkable phenomena when placed in relation 
with light and darkness. 

150. 

The highest degree of light, such as that of 
the sun, of phosphorus burning in oxygen, is 
dazzling and colourless: so the light of the 
fixed stars is for the most part colourless. This 
light, however, seen through a medium but very 
slightly thickened, appears to us yellow. If the 
density of such a medium be increased, or if its 
volume become greater, we shall see the light 
gradually assume a yellow-red hue, which at 
last deepens to a ruby-colour. — Note L. 



Digitized by 



Google 



62 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

15L 

If on the other hand darkness is seen through 
a semi-transparent mediuni, which is itself illu^ 
mined hy a light striking on it, a blue colour 
appears : this becomes lighter and paler as the 
density of the medium is increased, but on the 
contrary appears darker and deeper the more 
transparent the medium becomes : in the least 
degree of dimness short of absolute transpa- 
rence, always supposing a perfectly colourless 
medium, this deep blue approaches the most 
beautiful violet 

162. 

If this effect takes place in the eye as here de- 
scribed, and may thus be pronounced to be sub- 
jective, it remains further to convince ourselves 
of this by objective phenomena. For a light 
thus mitigated and subdued illumines all objects 
in like manner with a yellow, yellow-red, or 
red hue ; and, although the effect of darkness 
through the non-transparent medium does not 
exhibit itself so powerfully, yet the blue sky 
displays itself in the camera obscura very dis- 
tinctly on white paper, as well as every other 
material colour. 

163. 
In examining the cases in which this impor- 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 63 

taDt leading phenomenon appears, we naturally 
mention the atmospheric colours first : most of 
these may be here introduced in order. 

154. 

The sun seen through a certain degree of 
vapour appears with a yellow disk ; the centre 
is often dazzlingly yellow when the edges are 
already red. The orb seen through a thick 
yellow mist appears ruby-red (as was the case 
in 1 794, even in the north) ; the same appear- 
ance is still more decided, owing to the state of 
the atmosphere, when the scirocco prevails in 
southern climates: the clouds generally sur- 
rounding the sun in the latter case are of the 
same colour, which is reflected again on all 
objects. 

The red hues of morning and evening are 
owing to the same cause. The sun is announced 
by a red light, in shining through a greater mass 
of vapours. The higher he rises, the yellower 
and brighter the light becomes. 

166. 
If the darkness of infinite space is seen through 
atmospheric vapours illumined by the day-light, 
the blue colout appears. On high mountains 
the sky appears by day intensely blue, owing to 
the few thin vapours that float before the end- 
less dark space : as soon as we descend in the 



Digitized by 



Google 



64 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

valleys, the blue becomes lighter ; till at last, in 
certain regions, and in consequence of increasing 
vapours, it altogether changes to a very pale 
blue. 

156. 

The mountains, in like manner, appear to us 
blue ; for, as we see them at so great a distance 
that we no longer distinguish the local tints, 
and as no light reflected from their surface acts 
on our vision, they are equivalent to mere dark 
objects, which, owing to the interposed vapours, 
appear blue. 

157. 

So we find the shadowed parts of nearer ob- 
jects are blue when the air is charged with thin 
vapours. 

158. 

The snow-mountains, on the other hand, at a 
great distance, still appear white, or approaching 
to a yellowish hue, because they act on our eyes 
as brightness seen through atmospheric vapour. 

159. 

The blue appearance at the lower part of the 
flame of a candle belongs to the same class of 
phenomena. If the flame be held before a white 
ground, no blue will be seen, but this colour 
will immediately appear if the flame is opposed 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 65 

to a black ground. This phenomenon may be 
exhibited most strikingly with a spoonful of 
lighted spirits of wine. We may thus consider 
the lower part of the flame as equivalent to the 
vapour which, although infinitely thin, is still 
apparent before the dark surface ; it is so thin, 
that one may easily see to read through it : on 
the other hand, the point of the flame which 
conceals objects from our sight is to be consi- 
dered as a self-illuminating body. 

160. 

Lastly, smoke is also to be considered as a 
semi-transparent medium, which appears to us 
yellow or reddish before a light ground, but blue 
before a dark one. 

161. 

If we now turn our attention to fluid mediums, 
we find that water, deprived in a very slight 
d^ree of its transparency, produces the same 
efiects. 

162. 

The infusion of the lignum nephriticum (gui- 
landina Linnsei), which formerly excited so much 
attention, is only a semi-transparent liquor, 
which in dark wooden cups must appear blue, 
but held towards the sun in a transparent glass 
must exhibit a yellow appearance. 



Digitized by 



Google 



66 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

163. 

A drop of scented water, of spirit varnish, of 
several metallic solutions, may be employed to 
give various degrees of opacity to water for such 
experiments. Spirit of soap perhaps answers 
best. 

164. 

The bottom of the sea appears to divers of a 
red colour in bright sunshine : in this case the 
water, owing to its depth, acts as a semi-trans- 
parent medium. Under these circumstances, 
they find the shadows green, which is the com- 
plemental colour. 

165. 

Among solid mediums the opal attracts our 
attention first: its colours are, at least, partly 
to be explained by the circumstance that it is, 
in fact, a semi-transparent medium, through 
which sometimes light, sometimes dark, sub- 
strata are visible. 

166. 

For these experiments, however, the opal- 
glass (vitrum astroides, girasole) is the most 
desirable material. It is prepared in various 
ways, and its semi-opacity is produced by me- 
tallic oxydes. The same effect is produced also 
by melting pulverised and calcined bones toge- 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 67 

ther with the glass^ ou which account it is also 
known by the name of beinglas ; but, prepared 
in this mode, it easily becomes too opaque. 

167. 

This glass may be adapted for experiments in 
various ways : it may either be made in a very 
slight degree non-transparent, in which case the 
light seen through various layers placed one 
upon the other may be deepened from the lightest 
yellow to the deepest red, or, if made originally 
more opaque, it may be employed in thinner or 
thicker laminae. The experiments may be suc- 
cessfully made in both ways : in order, however^ 
to see the bright blue colour, the glass should 
neither be too opaque nor too thick. For, as it 
is quite natural that darkness must act weakly 
through the semi-transparent medium, so this 
medium, if too thick, soon approaches whiteness. 

168. 

Panes of glass throw a yellow light on objects 
through those parts where they happen to be 
semi-opaque, and these same parts appear blue 
if we look at a dark object through them. 

169. 

Smoked glass may be also mentioned here, 
and is, in like manner, to be considered as a 
semi-opaque medium. It exhibits the sun more 

f2 



Digitized by 



Google 



68 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

or less ruby-coloured ; and, although this appear- 
ance may be attributed to the black-brown 
colour of the soot, we may still convince our- 
selves that a semi-transparent medium here acts 
if we hold such a glass moderately smoked, and 
lit by the sun on the unsmoked side, before a 
dark object, for we shall then perceive a bluish 
appearance. 

170. 

A striking experiment may be made in a 
dark room with sheets of parchment. If we 
fasten a piece of parchment before the opening 
in the window-shutter when the sun shines, it 
will appear nearly white ; by adding a second, 
a yellowish colour appears, which still increases 
as more leaves are added, till at last it changes 
to red. 

171. 

A similar effect, owing to the state of the 
crystalline lens in milky cataract, has been 
already adverted to (131). 

172. 

Having now, in tracing these phenomena, 
arrived at the effect of a degree of opacity 
scarcely capable of transmitting light, we may 
here mention a singular appearance which was 
owing to a momentary state of this kind. 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 69 

A portrait of a celebrated theologian had 
been painted some years before the circum- 
stance to which we allude, by an artist who 
was known to have considerable skill in the 
management of his materials. The very reve- 
rend individual was represented in a rich velvet 
dress, which was not a little admired, and which 
attracted the eye of the spectator almost more 
than the face. The picture, however, from the 
effect of the smoke of lamps and dust, had lost 
much of its original vivacity. It was, therefore, 
placed in the hands of a painter, who was to 
clean it, and give it a fresh coat of varnish. 
This person began his operations by carefully 
washing the picture with a sponge : no 
sooner, however, had he gone over the surface 
once or twice, and wiped away the first dirt, 
than to his amazement the black velvet dress 
changed suddenly to a light blue plush, which 
gave the ecclesiastic a very secular, though some- 
what old-fashioned, appearance. The painter 
did not venture to go on with his washing : he 
could not comprehend how a light blue should 
be the ground of the deepest black, still less 
how he could so suddenly have removed a glaz- 
ing colour capable of converting the one tint 
to the other. 

At all events, he was not a little disconcerted 
at having spoilt the picture to such an extent. 
Nothing to characterize the ecclesiastic re- 



Digitized by 



Google 



\ 
70 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

mained but the richly-curled round wig, which 
made the exchange of a faded plush for a hand- 
some new velvet dress far from desirable. 
Meanwhile, the mischief appeared irreparable, 
and the good artist, having turned the picture to 
the wall, retired to rest with a mind ill at ease. 
But what was his joy the next morning, when, 
on examining the picture, he beheld the black 
velvet dress again in its full splendour. He 
could not refrain from again wetting a comer, 
upon which the blue colour again appeared, and 
after a time vanished. On hearing of this phe- 
nomenon, I went at once to see the miraculous 
picture. A wet sponge was passed over it in 
my presence, and the change quickly took place. 
I saw a somewhat faded, but decidedly light 
blue plush dress, the folds under the arm being 
indicated by some brown strokes. 

I explained this appearance to myself by the 
doctrine of the semi-opaque medium. The 
painter, in order to give additional depth to his 
black, may have passed some particular varnish 
over it : on being washed, this varnish imbibed 
some moisture, and hence became semi-opaque, 
in consequence of which the black underneath 
immediately appeared blue. Perhaps those 
who are practically acquainted with the effect 
of varnishes may, through accident or con- 
trivance, arrive at some means of exhibiting this 
singular appearance, as an experiment, to those 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 71 

who are fond of investigating natural pheno- 
mena. Notwithstanding many attempts, I 
could not myself succeed in re-producing it. 

173. 

Having now traced the most splendid in- 
stances of atmospheric appearances, as well as 
other less striking yet sufficiently remarkable 
cases, to the leading examples of semi-trans- 
parent mediums, we have no doubt that atten- 
tive observers of nature will carry such re- 
searches further, and accustom themselves to 
trace and explain the various appearances 
which present themselves in every-day experi- 
ence on the same principle : we may also hope 
that such investigators will provide themselves 
with an adequate apparatus in order to place 
remarkable facts before the eyes of others who 
may be desirous of information. 

174! 

We venture, once for all, to call the leading 
appearance in question, as generally described 
in the foregoing pages, a primordial and ele- 
mentary phenomenon ; and we may here be 
permitted at once to state what we understand 
by the term. 

175. 
The circumstances which come under our notice 
in ordinary observation are, for the most part, in- 
sulated cases, which, with some attention, admit 



Digitized by 



Google 



72 DIOPTRICAL COLOURS OF THE FIRST CLASS. 

of being classed under general leading facts. 
These again range themselves under theoretical 
rubrics which are more comprehensive, and 
through which we become better acquainted 
with certain indispensable conditions of appear- 
ances in detail. From henceforth everything is 
gradually arranged under higher rules and laws, 
which, however, are not to be made intelligible 
by words and hypotheses to the understanding 
merely, but, at the same time, by real phenomena 
to the senses. We call these primordial phe- 
nomena, because nothing appreciable by the 
senses lies beyond them, on the contrary, they 
are perfectly fit to be considered as a fixed point 
to which we first ascended, step by step, and 
from which we may, in like manner, descend to 
the commonest case of every-day experience. 
Such an original phenomenon is that which has 
lately engaged our attention. We see on the 
one side light, brightness ; on the other dark- 
ness, obscurity : we bring the semi-transparent 
medium between the two, and from these con- 
trasts and this medium the colours develop 
themselves, contrasted, in like manner, but soon, 
through a reciprocal relation, directly tending 
again to a point of union.^ 

* That is (according to the author's statement 1 50. 151.) both 
tend to red ; the yellow deepening to orange as the comparatively 
dark medium is thickened before brightness ; the blue deepening 
to violet as the light medium is thinned before darkness. — ^T. 



Digitized by 



Google 



DIOPTRICAL COLOURS OF THE FIRST CLASS. 73 
176. 

With this conyiction we look upon the mistake 
that has been committed in the investigation of 
this subject to be a very serious one, inasmuch 
as a secondary phenomenon has been thus 
placed higher in order — the primordial phe- 
nomenon has been degraded to an inferior place ; 
nay, the secondary phenon^enon has been placed 
at the head, a compound effect has been treated 
as simple, a simple appearance as compound : 
owing to this contradiction, the most capricious 
complication and perplexity have been intro- 
duced into physical inquiries, the effects of 
which are still apparent. 

177. 

But when even such a primordial phenomenon 
is arrived at, the evil still is that we refuse to 
recognise it as such^ that we still aim at some- 
thing beyond, although it would become us to 
confess that we are arrived at the limits of ex- 
perimental knowledge. Let the observer of 
nature suffer the primordial phenomenon to re- 
main undisturbed in its beauty; let the phi- 
losopher admit it into his department, and he 
will find that important elementary facts are a 
worthier basis for further operations than insu- 
lated cases, opinions, and hypotheses.-r-Note M. 



Digitized by 



Google 



76 DIOPTRICAL COLOURS 

tention was called to the degree of opacity in 
the medium. 

183. 

Thus the different degrees of opacity in so- 
called transparent mediums, nay, even other 
physical and chemical properties belonging to 
them, are known to our vision by means of re- 
fraction, and invite us to make further trials in 
order to penetrate more completely by physical 
and chemical means into those secrets which are 
already opened to our view on one side. 

184. 

Objects seen through mediums more or less 
transparent do not appear to us in the place 
which they should occupy according to the laws 
of perspective. On this fact the dioptrical 
colours of the second class depend. 

185. 

Those laws of vision which admit of being 
expressed in mathematical formulae are based on 
the principle that, as light proceeds in straight 
lines, it must be possible to draw a straight line 
from the eye to any given object in order that it 
be seen. If, therefore, a case arises in which 
the light arrives to us in a bent or broken line, 
that we see the object by means of a bent or 
broken line, we are at once informed that the 



Digitized by 



Google 



OF THE SECOND CLASS.— REFRACTION. 77 

medium between the eye and the object is 
denser, or that it has assumed this or that 
foreign nature. 

186. 

This deviation from the law of right-lined 
vision is known by the general term of refrac- 
tion ; and, although we may take it for granted 
that our readers are sufficiently acquainted with 
its effects, yet we will here once more briefly 
exhibit it in its objective and subjective point 
of view. 

187. 

Let the sun shine diagonally into an empty 
cubical vessel, so that the opposite side be il- 
lumined, but not the bottom : let water be then 
poured into this vessel, and the direction of the 
light will be immediately altered ; for a part of 
the bottom is shone upon. At the point where 
the light enters the thicker medium it deviates 
from its rectilinear direction, and appears broken : 
hence the phenomenon is called the breaking 
(brechung) or refraction. Thus much of the 
objective experiment. 

188. 
We arrive at the subjective fact in the follow- 
ing mode : — Let the eye be substituted for the 
sun : let the sight be directed in like manner 



Digitized by 



Google 



80 REFEACTION WITHOUT 

194. 

And now» in order to conduct our observations, 
with as much exactness as possible, and to avoid 
all confusion and ambiguity, we confine ourselves 
at first to 



SUBJECTIVE EXPERIMENTS, 

in which, namely, the object is seen by the ob- 
server through a refracting medium. As soon 
as we have treated these in due series, the ob- 
jective experiments will follow in similar order. 



XII. 

REFRACTION WITHOUT THE APPEARANCE OF COLOUR. 

195. 

Refraction can visibly take place without our 
perceiving an appearance of colour. To what- 
ever extent a colourless or uniformly coloured 
surface may be altered as to its position by re- 
fraction, no colour consequent upon refraction 
appears within it, provided it has no outline or 
boundary. We may convince ourselves of this 
in various ways. 



Digitized by 



Google 



THE APPEARANCE OF COLOUR. 81 

196. • 
Place a glass cube on any larger surface, 
and look through the glass perpendicularly or 
obliquely, the unbroken surface opposite the eye 
appears altogether raised, but no colour exhibits 
itself. If we look at a pure grey or blue sky or 
a uniformly white or coloured wall through a 
prism, the portion of the surface which the eye 
thus embraces will be altogether changed as to 
its position, without our therefore observing the 
smallest appearance of colour. 



XIII. 

CONDITIONS OF THE APPEARANCE OF COLOUR. 
197. 

Although in the foregoing experiments we 
have found all unbroken surfaces, large or small, 
colourless, yet at the outlines or boundaries, 
where the surface is relieved upon a darker or 
lighter object, we observe a coloured appearance. 

198. 

Outline, as well as surface, is necessary to 
constitute a figure or circumscribed object. We 
therefore express the leading fact thus : circum- 
scribed objects must be displaced by refraction 
in order to the exhibition of an appearance of 
colour. 

G 



Digitized by 



Google 



82 CONDITIONS OF 

" 199. 

We place before us the simplest object, a light 
disk on a dark ground (a).* A displacement 
occurs with regard to this object, if we appa- 
rently extend its outline from the centre by mag- 
nifying it. This may be done with any convex 
glass, and in this case we see a blue edge (b). 

200. 

We can, to appearance, contract the circum- 
ference of the same light disk towards the centre 
by diminishing the object ; the edge will then 
appear yellow (c). This may be done with a 
concave glass, which, however, should not be 
ground thin like common eye-glasses, but must 
have some substance. In order, however, to 
make this experiment at once with the convex 
glass, let a smaller black disk be inserted within 
the light disk on a black ground. If we magnify 
the black disk on a white ground with a con- 
vex glass, the same result takes place as if we 
diminished the white disk ; for we extend the 
black outline upon the white, and we thus per- 
ceive the yellow edge together with the blue 
edge (D). 

201. 

These two appearances, the blue and yellow, 
exhibit themselves in and upon the white : they 

♦ Plate 2, fig. 1. 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 



THE APPEARANCE OF COLOUR. 83 

both assume a reddish hue, in proportion as^ 
they mingle with the black.* 

202. 

In this short statement we have described the 
primordial phenomena of all appearance of co- 
lour occasioned by refraction. These undoubt- 
edly may be repeated, varied, and rendered 
more striking ; may be combined, complicated, 
confused ; but, after all, may be still restored 
to their original simplicity. 

203. 

In examining the process of the experiment 
just given, we find that in the one case we have, 
to appearance^ extended the white edge upon the 
dark surface ; in the oiher we have extended the 
dark edge upon the white surface, supplanting 
one by the other, pushing one over the other. 
We will now endeavour, step by step, to analyse 
these and similar cases. 

204. 

If we cause the white disk to move, in appear- 
ance, entirely from its place, which can be done 

* The author has omitted the orange and purple in the co- 
loured diagrams which illustrate these first experiments, from a 
wish prohahly to present the elementary contrast, on which he 
lays a stress, in greater simplicity. The reddish tinge would he 
apparent, as stated ahove, where the hlue and yellow are in con- 
tact with the black.— T. 

g2 



Digitized by 



Google 



84 CONDITIONS OF 

effectually by prisms, it will be coloured ac- 
cording to the direction in which it apparently 
moves, in conformity with the above laws. If 
we look at the disk a* through a prism, so that 
it appear moved to 6, the outer edge will 
appear blue and blue-red, according to the law 
of the figure b (fig. 1), the other edge being 
yellow, and yellow-red, according to the law of 
the figure c (fig, 1). For in the first case the 
white figure is, as it were, extended over the 
dark boundary, and in the other case the dark 
boundary is passed over the white figure. The 
same happens if the disk is, to appearance, 
moved from a to e, from a to d, and so throughout 
the circle. 

205. 

As it is with the simple effect, so it is with 
more complicated appearances. If we look 
through a horizontal prism (aif ) at a white disk 
placed at some distance behind it at e, the disk 
will be raised to /, and coloured according to 
the above law. If we remove this prism, and 
look through a vertical one (c d) at the same 
disk, it will appear at A, and coloured accord- 
ing to the same law. If we place the two 
prisms one upon the other, the disk will appear 
displaced diagonally, in conformity with a ge- 
neral law of nature, and will be coloured as 

♦ Plate 2, fig. 2. t Pl^te 2, fig. 4. 



Digitized by 



Google 



THE APPEARANCE OF COLOUR. 85 

before ; that is, according to its movement in the 
direction, e. g. : * 

206, 

If we attentively examine these opposite co- 
loured edges, we find that they only appear in 
the direction of the apparent change of place. 
A round figure leaves us in some degree uncer- 
tain as to this : a quadrangular figure removes 
all doubt. 

207. 

The quadrangular figure a,t moved in the 
direction ab, or ad^ exhibits no colour on the 
sides which are parallel with the direction in 
which it moves: on the other hand, if moved 
in the direction ae, parallel with its diagonal, 
all the edges of the figure appear coloured.^ 

208. 

Thus, a former position (203) is here con- 
firmed; viz. to produce colour, an object must 
be so displaced that the light edges be appa- 
rently carried over a dark surface, the dark 
edges over a light surface, the figure over its 
boundary, the boundary over the figure. But 

* In this case, according to the author, the refracting medium 
being increased in mass, the appearance of colour is increased, 
and the displacement is greater. — ^T. 

t Plate 2, fig. 3. 

I Fig. 2, plate 1, contains a variety of forms, which, when 
viewed through a prism, are intended to illustrate the statement 
in this and the following paragraph. 



Digitized by 



Google 



86 CONDITIONS UNDER WHICH THE 

if the rectilinear boundaries of a figure could be 
indefinitely extended by refraction, so that figure 
and background might only pursue their course 
next, but not over each other, no colour would 
appear, not even if they were prolonged to 
infinity. 



XIV. 

CONDITIONS UNDER WHICH THE APPEARANCE OF 
COLOUR INCREASES. 

209. 

We have seen in the foregoing experiments 
that all appearance of colour occasioned by re- 
fraction depends on the condition that the 
boundary or edge be moved in upon the object 
itself, or the object itself over the ground, that 
the figure should be, as it were, carried over 
itself, or over the ground. And we shall now 
find that, by increased displacement of the object, 
the appearance of colour exhibits itself in a 
greater degree. This takes place in subjective 
experiments, to which, for the present, we con- 
fine ourselves, under the following conditions. 

210. 

First, if, in looking through parallel mediums, 
the eye is directed more obliquely. 

Secondly, if the surfaces of the medium are 
no longer parallel, but form a more or less acute 
angle. 



Digitized by 



Google 



APPEARANCE OF COLOUR INCREASES. 87 

Thirdly, owing to the increased proportion of 
the medium, whether parallel mediums be in- 
creased in size, or whether the angle be in- 
creased, provided it does not attain a right angle. 

Fourthly, owing to the distance of the eye 
armed with a refracting medium from the object 
to be displaced. 

Fifthly, owing to a chemical property that 
may be communicated to the glass, and which 
may be afterwards increased in effect. 

211. 

The greatest change of place, short of consi- 
derable distortion of the object, is produced by 
means of prisms, and this is the reason why the 
appearance of colour can be exhibited most 
powerfully through glasses of this form. Yet 
we will not, in employing them, suffer ourselves 
to be dazzled by the splendid appearances they 
exhibit, but keep the above well-established, 
simple principles calmly in view, 

212. 

The colour which is outside, or foremost, in 
the apparent change of an object by refraction, 
is always the broader, and we will henceforth 
call this a border : the colour that remains next 
the outline is the narrower, and this We will caU 
an edge. 



Digitized by 



Google 



88 CONDITIONS UNDER WHICH THE 

213. 

If we moye a dark boundary towards a light 
surface, the yellow broader border is foremost, 
and the narrower yellow-red edge follows close 
to the outline. If we move a light boundary 
towards a dark surface, the broader violet border 
is foremost, and the narrower blue edge follows. 

214. 
If the object is large, its centre remains un- 
coloured. Its inner surface is then to be consi- 
dered as unlimited (195) : it is displaced, but 
not otherwise altered : but if the object is so 
narrow, that under the above conditions the 
yellow border can reach the blue edge, the space 
between the outlines will be entirely covered 
with colour. If we make this experiment with 
a white stripe on a black ground,* the two ex- 
tremes will presently meet, and thus produce 
green. We shall then see the following series 
of colours : — 

Yellow*red. 

Yellow. 

Green. 

Blue. 

Blue-red. 

215. 
If we place a black band, or stripe, on white 
paper,t the violet border will spread till it meets 

♦ Plate 2, fig. 5, left, f Plate 2, fig. 5, rinht. 



Digitized by 



Google 



APPEARANCE OF COLOUR INCREASES. 89 

the yellow-red edge. In this case the inter- 
mediate black is effaced (as the intermediate 
white was in the last experiment), and in its 
stead a splendid pure red will appear.* The 
series of colours will now be as follows : — 

Blue. 

Blue-red. 

Red. 

Yellow-red. 

Yellow. 

216. 
The yellow and blue, in the first case (214),- 
can by degrees meet so fully, that the two 
colours blend entirely in green, and the order 
will then be. 

Yellow-red. 
Green. 
BluQ-red. 
In the second case (215), under similar cir- 
cumstances, we see only 
Blue. 
Red. 
Yellow. 
This appearance is best exhibited by refract- 
ing the bars of a window when they are relieved 
on a grey sky.f 

* This pure red, the union of orange and violet, is considered 
by the author the maximum of the coloured appearance : he has 
appropriated the term purpur to it. See paragraph 703, and 
note.—T. 

t The bands or stripes in fig. 4, plate 1, when viewed through 
a prism, exhibit the colours represented in plate 2, fig. 5. 



Digitized by 



Google 



00 EXPLANATION OF THE FOKEGOING PHENOMENA. 

217. 

In all this we are never to forget that this 
appearance is not to be considered as a complete 
or final state, but always as a progressive, in- 
creasing, and, in many senses, controllable ap- 
pearance. Thus we find that, by the negation 
of the above five conditions, it gradually de- 
creases, and at last disappears altogether. 



XV. 

EXPLANATION OF THE FOREGOING PHENOMENA. 
218. 

Before we proceed further, it is incumbent on 
us to explain the first tolerably simple pheno- 
menon, and to show its connexion with the 
principles first laid down, in order that the ob- 
server of nature may be enabled clearly to com- 
prehend the more complicated appearances that 
follow. 

219. 

In the first place, it is necessary to remember 
that we have to do with circumscribed objects. 
In the act of seeing, generally, it is the circum- 
scribed visible which chiefly invites our obser- 
vation; and in the present instance, in speak- 
ing of the appearance of colour, as occasioned 
by' refraction, the circumscribed visible, the de- 
tached object solely occupies our attention. 



Digitized by 



Google 



EXPLANATION OF THE FOREGOING PHENOMENA. 91 
220. 

For our chromatic exhibitioos we can, how- 
ever, divide objects generally into primary and 
secondary. The expressions of themselves de- 
note what we understand by them, but our 
meaning will be rendered still more plain by 
what follows. 

221. 
Primary objects may be considered firstly as 
original, as images which are impressed on the 
eye by things before it, and which assure us of 
their reality. To these the secondary images 
may be opposed as derived images, which remain 
in the organ when the object itself is taken 
away ; those apparent after-images, which have 
been circumstantially treated of in the doctrine 
of physiological colours. 

222. 
The primary images, again, may be consi- 
dered as direct images, which, like the original 
impressions, are conveyed immediately from tlie 
object to the eye. In contradistinction to these, 
the secondary images may be considered as in- 
direct^ being only conveyed to us, as it were, at 
second-hand from a reflecting surface. These 
are the mirrored, or catoptrical, images, which 
in certain cases can also become double images : 

223. 
When, namely, the reflecting body is trans- 



Digitized by 



Google 



92 EXPLANATION OF THE FOREGOING PHENOMENA. 

parent, and has two parallel surfaces, one behind 
the other : in such a case, an image may be re- 
flected to the eye from both surfaces, and thus 
arise double images, inasmuch as the upper 
image does not quite cover the under one : this 
may take place in various ways. 

Let a playing-card be held before a mirror. 
We shall at first see the distinct image of the 
card, but the edge of the whole card, as well as 
that of every spot upon it, will be bounded on 
one side with a border, which is the beginning 
of the second reflection. This efiect varies in 
difierent mirrors, according to the difierent 
thickness of the glass, and the accidents of 
polishing. If a person wearing a white waist- 
coat, with the remaining part of his dress dark, 
stands before certain mirrors, the border appears 
very distinctly, and in like manner the metal 
buttons on dark cloth exhibit the double reflec- 
tion very evidently. 

224. 

The reader who has made himself acquainted 
with our former descriptions of experiments (80) 
will the more readily follow the present state- 
ment. The window-bars reflected by plates of 
glass appear double, and by increased thickness 
of the glass, and a due adaptation of the angle 
of reflection, the two reflections may be entirely 
separated from each other. So a vase full of 



Digitized by 



Google 



EXPLANATION OF THE FOREGOING PHENOMENA. 93 

water, with a plane mirror-like bottom, reflects 
any object twice, the two reflections being 
more or less separated under the same con- 
ditions. In these cases it is to be observed that, 
where the two reflections cover each other, 
the perfect vivid image is reflected, but where 
they are separated they exhibit only weak, 
transparent, and shadowy images. 

225. 

If we wish to know which is the under and 
which the upper image, we have only to take a 
coloured medium, for then a light object re- 
flected from the under surface is of the colour 
of the medium, while that reflected from the 
upper surface presents the complemental colour. 
With dark objects it is the reverse ; hence black 
and white surfaces may be here also conveni- 
ently employed. How easily the double images 
assume and evoke colours will here again be 
striking. 

226. 

Thirdly, the primary images may be con- 
sidered as principal images, while the secondary 
can be, as it were, annexed to these as accessary 
images. Such an accessory image produces a sort 
of double form ; except that it does not separate 
itself from the principal object, although it may 
be said to be always endeavouring to do so. It is 



Digitized by 



Google 



94 EXPLANATION OF THE FOREGOING PHENOMENA. 

with secondary images of this last description 
that we have to do in prismatic appearances. 

227. 

A surface without a boundary exhibits no 
appearance of colour when refracted (195)* 
Whatever is seen must be circumscribed by an 
outline to produce this effect. In other words 
a figure, an object, is required ; this object 
undergoes an apparent change of place by re- 
fraction : the change is however not complete, 
not clean, not sharp ; but incomplete, inasmuch 
as an accessor}^ image only is produced. 

228. 

In examining every appearance of nature, 
but especially in examining an important and 
striking one, we should not remain in one spot, 
we should not confine ourselves to the insulated 
fact, nor dwell on it exclusively, but look round 
through all nature to see where something simi- 
lar, something that has affinity to it, appears : 
for it is only by combining analogies that we 
gradually arrive at a whole which speaks for 
itself, and requires no further explanation. 

229. 

Thus we here call to mind that in certain 
cases refraction unquestionably produces double 
images, as is the case in Iceland spar : similar 



Digitized by 



Google 



EXPLANATION OF THE FOREGOING PHENOMENA. 95 

double images are also apparent in cases of re- 
fraction through large rock crystals, and in 
other instances ; phenomena which have not 
hitherto been sufficiently observed.* 

230. 

But since in the case under consideration 
(227) the question relates not to double but to 
accessory images, we refer to a phenomenon 
already adverted to, but not yet thoroughly 
investigated. We allude to an earlier experi- 
ment, in which it appeared that a sort of con- 
flict took place in regard to the retina between 
a light object and its dark ground, and between 
a dark object and its light ground (16). The 
light object in this case appeared larger, the 
dark one smaller. 

231. 

By a more exact observation of this phena- 
menon we may remark that the forms are not 
sharply distinguished from the ground, but that 
they appear with a kind of grey, in some de- 
gree, coloured edge ; in short, with an accessory 
image. If, then, objects seen only with the 
naked eye produce such effects, what may not 
take place when a dense medium is interposed? 
It is not that alone which presents itself to us 

* The date of the publication, 1810, is sometimes to be remem- 
bered. — ^T. 



Digitized by 



Google 



96 EXPLANATION OF THE FOREGOING PHENOMENA. 

in obyious operation which produces and suffers 
effects, but likewise all principles that have a 
mutual relation only of some sort are efficient 
accordingly, and indeed often in a very high 
degree. 

232. 

Thus when refraction produces its effect on 
an object there appears an accessory image 
next the object itself: the real form thus re- 
fracted seems even to linger behind, as if resist- 
ing the change of place ; but the accessory image 
seems to advance, and extends itself more or 
less in the mode already shown (212 — 216), 

233. 

We also remarked (224) that in double 
images the fainter appear only half substan- 
tial, having a kind of transparent, evanescent 
character, just as the fainter shades of double 
shadows must always appear as half-shadows. 
These latter assume colours easily, and produce 
them readily (69), the former also (80) ; and the 
same takes place in the instance of accessory 
images, which, it is true, do not altogether quit 
the real object, but still advance or extend from 
it as half-substantial images, and hence can ap- 
pear coloured so quickly and so powerfully. 

234. 
That the prismatic appearance is in fact an 



Digitized by 



Google 



EXPLANATION OF THE FOREGOING PHENOMENA. 97 

accessory image we may convince ourselves in 
more than one mode. It corresponds exactly 
with the form of the object itself Whether the 
object be bounded by a straight line or a curve, 
indented or waving, the form of the accessory 
image corresponds throughout exactly with the 
form of the object* 

235. 

Again, not only the form but other qualities 
of the object are communicated to the accessory 
image. If the object is sharply relieved from 
its ground, like white on black, the coloured 
accessory image in like manner appears in its 
greatest force. It is vivid, distinct, and power- 
ful ; but it is most especially powerful when a 
luminous object is shown on a dark ground, 
which may be contrived in various ways. 

236. 

But if the object is but faintly distinguished 
from the ground, like grey objects on black or 
white, or even on each other, the accessory 
image is also faint, and, when the original differ- 
ence of tint or force is slight, becomes hardly 
discernible. 



* The forms in fig. 2, plate 1, when seen through a prisin, are 
again intended to exemplify this. In the plates to the original 
work curvilinear figures are added, but the circles, fig. 1, in the 
same plate, may answer the same end. — ^T. 

H 



Digitized by 



Google 



98 EXPLANATION OF THE FOREGOING PHENOMENA. 

237. 

The appearances which are obserrable when 
coloured objects are relieved on light, dark, or 
coloured grounds are, moreover, well worthy of 
attention. In this case a union takes place 
between the apparent colour of the accessory 
image and the real colour of the object ; a com- 
pound colour is the result, which is either assisted 
and enhanced by the accordance, or neutralised 
by the opposition of its ingredients. 

238. 

But the common and general characteristic 
both of the double and accessory image is semi- 
transparence. The tendency of a transparent 
medium to become only half transparent, or 
merely light-transmitting, has been before ad- 
verted to (147, 148), Let the reader assume 
that he sees within or through such a medium 
a visionary image, and he will at once pro- 
nounce this latter to be a semi-transparent image. 

239. 
Thus the colours produced by refraction may 
be fitly explained by the doctrine of the semi- 
transparent mediums. For where dark passes 
over light, as the border of the semi-transparent 
accessory image advances, yellow appears ; and, 
on the other hand, where a light outline passes 
over the dark background, blue appears (150, 
151). 



Digitized by 



Google 



EXPLANATION OF THE FOREGOING PHENOMENA. ^9 
240. 

The advancing foremost colour is always the 
broader. Thus the yellow spreads over the light 
with a broad border, but the yellow-red appears 
as a narrower stripe and is next the dark, ac- 
cording to the doctrine of augmentation^ as an 
eflfect of shade.* 

241. 

On the opposite side the condensed blue is 
next the edge, while the advancing border, 
spreading as a thinner veil over the black, pro- 
duces the violet colour, precisely on the princi- 
ples before explained in treating of semi-trans- 
parent mediums, principles which will hereafter 
be found equally efficient in many other cases. 

242. 

Since an analysis like the present requires to 
be confirmed by ocular demonstration, we beg 
every reader to make himself acquainted with 
the experiments hitherto adduced, not in a 
superficial manner, but fairly and thoroughly. 
We have not placed arbitrary signs before him 
instead of the appearances themselves; no 
modes of expression are here proposed for his 

* The author has before observed that colour is a degree of 
darkness, and he here means that increase of darkness, produced by 
transparent mediums, is, to a certain extent, increase of colour. — ^T. 

h2 



Digitized by 



Google 



100 EXPLANATION OF THE FOREGOING PHENOMENA. 

adoption which may be repeated for ever with- 
out the exercise of thought and without leading 
any one to think ; but we invite him to examine 
intelligible appearances, which must be present 
to the eye and mind, in order to enable him 
clearly to trace these appearances to their ori- 
gin, and to explain them to himself and to 
others. 



XVI. 

DECREASE OF THE APPEARANCE OF COLOUR. 
243. 

We need only take the five conditions (210) 
under which the appearance of colour increases 
in the contrary order, to produce the contrary or 
decreasing state ; it may be as well, however, 
briefly to describe and review the corresponding 
modifications which are presented to the eye. 

244. 

At the highest point of complete junction of 
the opposite edges, the colours appear as fol- 
lows (216) :— 

Yellow-red. Blue. 

Green. Red. 

Blue-red. Yellow. 



Digitized by 



Google 



DECREASE OF THE APPEARANCE OF COLOUR. 101 
245. 

Where the junction is less complete, the ap- 
pearance is as follows (214, 215) : — 

Yellow-red. Blue. 

Yellow. Blue-red. 

Green. Red. 

Blue. Yellow-red. 

Blue-red. Yellow. 

Here, therefore, the surface still appears 
completely coloured, but neither series is to be 
considered as an elementary series, always de- 
veloping itself in the same manner and in the 
same degrees; on the contrary, they can and 
should be resolved into their elements ; and, in 
doing this, we become better acquainted with 
their nature and character. 

246. 
These elements then are (199, 200, 201)— 



Yellow-red. 


Blue. 


Yellow. 


Blue-red. 


White. 


Black. 


Blue. 


Yellow-red 


Blue-red. 


Yellow. 



Here the surface itself, the original object, 
which has been hitherto completely covered, 
and as it were lost, again appears in the centre 
of the colours, asserts its right, and enables us 



Digitized by 



Google 



102 DECREASE OF THE APPEARANCE OF COLOUR. 

fully to recognise the secondary nature of the 
accessory images which exhibit themselves as 
'' edges " and " borders." — Note N. 

247. 

We can make these edges and borders as nar- 
row as we please ; nay, we can still have refrac- 
tion in reserve after having done away with all 
appearance of colour at the boundary of the 
object. 

Having now sufficiently investigated the ex- 
hibition of colour in this phenomenon, we repeat 
that we cannot admit it to be an elementary 
phenomenon. On the contrary, we have traced 
it to an antecedent and a simpler one ; we have 
derived it, in connexion with the theory of se- 
condary images, from the primordial pheno- 
menon of light and darkness, as affected or acted 
upon by semi-transparent mediums. Thus pre- 
pared, we proceed to describe the appearances 
which refraction produces on grey and coloured 
objects, and this will complete the section of 
subjective phenomena. 



Digitized by 



Google 



103 
XVII. 

GREY OBJECTS DISPLACED BY REFRACTION. 
248. 

Hitherto we have confined our attention to 
black and white objects relieved on respectively 
opposite grounds, as seen through the prism, 
because the coloured edges and borders are most 
clearly displayed in such cases. We now re- 
peat these experiments with grey objects, and 
again find similar results. 

249. 

As we called black the equivalent of dark- 
ness, and white the representative of light (18), 
so we now venture to say that grey represents 
half-shadow, which partakes more or less of 
light and darkness, and thus stands between 
the two. We invite the reader to call to mind 
the following facts as bearing on our present 
view. 

250. 

Grey objects appear lighter on a black than 
on a white ground (33) ; they appear as a light 
on a black ground, and larger ; as a dark on the 
white ground, and smaller. (16.) 



Digitized by 



Google 



104 GREY OBJECTS DISPLACED BY REFRACTION. 

251. 

The darker the grey the more it appears as 
a faint light on black, as a strong dark on white, 
and vice versd ; hence the accessory images of 
dark-grey on black are faint, on white strong : 
so the accessory images of light-grey on white 
are faint, on black strong. 

252. 

Grey on black, seen through the prism^ will 
exhibit the same appearances as white on black ; 
the edges are coloured according to the same 
law, only the borders appear fainter. If we 
relieve grey on white, we have the same edges 
and borders which would be produced if we saw 
black on white through the prism. — Note O. 

253. 

Various shades of grey placed next each 
other in gradation will exhibit at their edges, 
either blue and violet only, or red and yellow 
only, according as the darker grey is placed 
over or under. 

254. 

A series of such shades of grey placed hori- 
zontally next each other will be coloured con- 
formably to the same law according as the whole 
series is relieved, on a black or white ground 
above or below. 



Digitized by 



Google 



GREY OBJECTS DISPLACED BY REFRACTION. 105 
255. 

The observer may see the phenomena ex- 
hibited by the prism at one glance, by enlarging 
the plate intended to illustrate this section.* 

256. 

It is of great importance duly to examine and 
consider another experiment in which a grey 
object is placed partly on a black and partly on 
a white surface, so that the line of division 
passes vertically through the object. 

257. 

The colours will appear on this grey object 
in conformity with the usual law, but according 
to the opposite relation of the light to the dark, 
and will be contrasted in a line. For as the 
grey is as a light to the black, so it exhibits the 
red and yellow above the blue and violet below : 
again, as the grey is as a dark to the white, the 
blue and violet appear above the red and yellow 
below. This experiment will be found of great 
importance with reference to the next chapter. 

* It has been thought unnecessary to give all the examples in 
the plate alluded to, but the leading instance referred to in the 
next paragraph will be found in plate 3, fig. I. The grey square 
when seen through a prism will exhibit the effects described in 
par. 251.— T. 



Digitized by 



Google 



106 
XVIIl. 

COLOURED OBJECTS DISPLACED BY REFRACTION. 
258. 

An unlimited coloured surface exhibits 
no prismatic colour in addition to its own hue, 
thus not at all differing from a blacky white^ or 
grey surface. To produce the appearance of 
colour, light and dark boundaries must act on it 
either accidentally or by contrivance. Hence 
experiments and observations on coloured sur- 
faces, as seen through the prism, can only be 
made when such surfaces are separated by an 
outline from another differently tinted surface, 
in short when circumscribed objects are coloured, 

259. 

All colours, whatever they may be, correspond 
so far with grey, that they appear darker than 
white and lighter than black. This shade-like 
quality of colour (erxiepov) has been already al- 
luded to (69) , and will become more and more 
evident. If then we begin by placing coloured 
objects on black and white surfaces, and ex- 
amine them through the prism, we shall again 
have all that we have seen exhibited with grey 
surfaces. 



Digitized by 



Google 



Digitized by 



Google 



-fv ^ in 



Fig Z 



Digitized by 



Google 



COLOURED OBJECTS DISPLACED BY REFRACTION. 107 
260. 

If we displace a coloured object by refraction, 
there appears, as in the case of colourless ob- 
jects and according to the same laws, an acces- 
sory image. This accessory image retains, as 
far as colouil* is concerned, its usual nature, and 
acts on one side as a blue and blue-red, on the 
opposite side as a yellow and yellow-red. Hence 
the apparent colour of the edge and border will 
be either homogeneous with the real colour of 
the object, or not so. In the first case the ap- 
parent image identifies itself with the real one, 
and appears to increase it, while, in the second 
case, the real image may be vitiated, rendered 
indistinct, and reduced in size by the apparent 
image. We proceed to review the cases in 
which these efiects are most strikingly exhibited. 

261. 

If we take a coloured drawing enlarged from 
the plate, which illustrates this experiment,* 
and examine the red and blue squares placed 
next each other on a black ground, through the 
prism as usual, we shall find that as both colours 
are lighter than the ground, similarly coloured 
edges and borders will appear above and below, 

* Plate 3, fig. 1. The author always recommends making the 
experiments on an increased scale, in order to see the prismatic 
effects distinctly. 



Digitized by 



Google 



108 COLOURED OBJECTS DISPLACED BY REFRACTION. 

at the outlines of botb« only they will not appear 
equally distinct to the eye. 

262. 

Red is proportionally much lighter on black 
than blue is. The colours of the edges will 
therefore appear stronger on the red than on 
the blue, which here acts as a dark-grey, but 
little diflTerent from black. (251.) 

263. 

The extreme red edge will identify itself with 
the vermilion colour of the square, which will 
thus appear a little elongated in this direction ; 
while the yellow border immediately underneath 
it only gives the red surface a more brilliant 
appearance, and is not distinguished without 
attentive observation. 

264. 

On the other hand the red edge and yellow 
border are heterogeneous with the blue square ; 
a dull red appears at the edge, and a dull green 
mingles with the figure, and thus the blue 
square seems, at a hasty glance, to be com- 
paratively diminished on this side. 

265. 

At the lower outline of the two squares a blue 
edge and a violet border will appear, and will 



Digitized by 



Google 



COLOURED OBJECTS DISPLACED BY REFRACTION. 109 

produce the contrary eflfect ; for the blue edge, 
which is heterogeneous with the warm red sur- 
face, will vitiate it and produce a neutral colour, 
so that the red on this side appears compara- 
tively reduced and driven upwards, and the 
violet border on the black is scarcely percep- 
tible. 

266. 

On the other hand, the blue apparent edge 
will identify itself with the blue square, and 
not only not reduce, but extend it. The blue 
edge and even the violet border next it have 
the apparent effect of increasing the surface, 
and elongating it in that direction. 

267. 

The effect of homogeneous and heterogeneous 
edges, as I have now minutely described it, is 
so powerful and singular that the two squares 
at the first glance seem pushed out of their re- 
lative horizontal position and moved in opposite 
directions, the red upwards, the blue down- 
wards. But no one who is accustomed to ob- 
serve experiments in a certain succession, and 
respectively to connect and trace them, will 
suffer himself to be deceived by such an unreal 
effect. 

268. 
A just impression with regard to this import- 



Digitized by 



Google 



110 COLOURED OBJECTS DISPLACED BY REFRACTION. 

ant phenomenon will, however, much depend 
on some nice and even troublesome conditions, 
which are necessary to produce the illusion in 
question. Paper should be tinged with vermi- 
lion or the best minium for the red square, and 
with deep indigo for the blue square. The blue 
and red prismatic edges will then unite imper- 
ceptibly with the real surfaces where they are 
respectively homogeneous ; where they are not, 
they vitiate the colours qf the squares without 
producing a very distinct middle tint. The real 
red should not incline too much to yellow, other- 
wise the apparent deep red edge above will be 
too distinct; at the same time it should be 
somewhat yellow, otherwise the transition to the 
yellow border will be too observable. The blue 
must not be light, otherwise the red edge will 
be visible, and the yellow border will produce 
a too decided green, while the violet border 
underneath would not give us the impression of 
being part of an elongated light blue square. 

269. 

All this will be treated more circumstantially 
hereafter, when we speak of the apparatus in- 
tended to facilitate the experiments connected 
with this part of our subject.* Every inquirer 



♦ Neither the description of the apparatus nor the recapitula- 
tion of the whole theory, so often alluded to by the author, were 
ever given. — ^T. 



Digitized by 



Google 



COLOURED obj:^cts displaced by refraction. Ill 

should prepare the figures himself, in order 
fairly to exhibit this specimen of ocular decep- 
tion, and at the same time to convince himself 
that the coloured edges, even in this case, can- 
not escape accurate examination. 

270. 

Meanwhile various other combinations, as 
exhibited in the plate, are fully calculated to 
remove all doubt on this point in the mind of 
every attentive observer. 

271. 

If, for instance, we look at a white square, 
next the blue one, on a black ground, the pris- 
matic hues of the opposite edges of the white, 
which here occupies the place of the red in the 
former experiment, will exhibit themselves in 
their utmost force. The red edge extends itself 
above the level of the blue almost in a greater 
degree than was the case with the red square 
itself in the former experiment. The lower blue 
edge, again, is visible in its full force next the 
white, while, on the other hand, it cannot be 
distinguished next the blue square. The violet 
border underneath is also much more apparent 
on the white than on the blue. 

272. 
If the observer now compares these double 



Digitized by 



Google 



1 1 2 COLOURED OBJECTS DISPLACED BY REFRACTION. 

squares, carefully prepared and arranged one 
above the other, the red with the white, the two 
blue squares together, the blue with the red, the 
blue with the white, he will clearly perceive the 
relations of these surfaces to their coloured 
edges and borders. 

273. 

The edges and their relations to the coloured 
surfaces appear still more striking if we look at 
the coloured squares and a black square on a 
white ground ; for in this case the illusion be* 
fore mentioned ceases altogether, and the effect 
of the edges is as visible as in any case that has 
come under our observation. Let the blue and 
red squares be first examined through the prism. 
In both the blue edge now appears above ; this 
edge, homogeneous with the blue surface, unites 
with it, and appears to extend it upwards, only 
the blue edge, owing to its lightness, is some- 
what too distinct in its upper portion ; the vio- 
let border underneath it is also sufficiently evi- 
dent on the blue. The apparent blue edge is, 
on the other hand, heterogeneous with the red 
square ; it is neutralised by [contrast, and is 
scarcely visible; meanwhile the violet border, 
uniting with the real red, produces a hue re- 
sembling that of the peach-blossom. 

274. 
If thus, owing to the above causes, the upper 



Digitized by 



Google 



COLOURED OBJECTS DISPLACED BY REFRACTION. 113 

outlines of these squares do not appear level 
with each other, the correspondence of the 
under outlines is the more observable i for since 
both colours, the red and the blue, are darks 
compared with the white (as in the former case 
they were light compared with the black), the 
red edge with its yellow border appears very 
distinctly under both. It exhibits itself under 
the warm red surface in its full force, and 
under the dark blue nearly as it appears under 
the black : as may be seen if we compare the 
edges and borders of the figures placed one 
above the other on the white ground. 

275. 
In order to present these experiments with 
the greatest variety and perspicuity, squares 
of various colours are so arranged* that 
the boundary of the black and white passes 
through them vertically. According to the 
laws now known to us, especially in their appli-^ 
cation to coloured objects, we shall find the 
squares as usual doubly coloured at each edge ; 
each square will appear to be split in two, and 
to be elongated upwards or downwards. We 
may here call to mind the experiment with the 
grey figure seen in like manner on the line of 
division between black and white (257). t 

♦ Plate iu. fig. 1. 

t The grey square is introduced in the same plate, fig. 1, above 
the coloured squares. 

I 



Digitized by 



Google 



114 COLOURED OBJECTS DISPLACED BY REFRACTION. 

276. 

A phenomenon was before exhibited, even to 
illusion, in the instance of a red and blue 
square on a black ground ; in the present expe* 
riment the elongation upwards and downwards 
of two diflferently coloured figures is apparent 
in the two halves of one and the same figure of 
one and the same colour. Thus we are still re^ 
ferred to the coloured ed^s and borders, and to 
the effects of their homogeneous and heteroge^ 
neous relations with respect to the real colours 
of the objects. 

277. 

I leave it to observers themselves to compare 
the various gradations of coloured squares, 
placed half on black half on white, only in- 
viting their attention to the apparent alteration 
which takes place in contrary directions; for 
red and yellow appear elongated upwards if on 
a black ground, downwards if on a white ; blue» 
downwards if on a black ground, upwards if on a 
white. All which, however, is quite in accordance 
with the diffusely detailed examples above given. 

278. 
Let the observer now turn the figures so that 
the before-mentioned squares placed on the line 
of division between black and white may be in 
a horizontal series ; the black above, the white 
underneath. On looking at these squares 



Digitized by 



Google 



COLOURED OBJECTS DISPLACED BY REFEAOTION. 115 

through the prism, he will observe that the red 
square gains by the addition of two red edges ; 
on more accurate examination he will observe 
the yellow border on the red figure, and the 
lower yellow border upon the white will be per- 
fectly apparent 

279. 

The upper red edge on the blue square is 
on the other hand hardly visible ; the yellow 
border next it produces a dull green by mingling 
with the figure; the lower red edge and the 
yellow border are displayed in lively colours. 

280. 
After observing that the red figure in these 
cases appears to gain by an addition on both 
sides, while the dark blue, on one side at least, 
loses something; we shall see the contrary 
efi*ect produced by turning the same figures up- 
side down, so that the white ground be above, 
the black below. 

281. 
For as the homogeneous edges and borders 
now appear above and below the blue square, 
this appears elongated, and a portion of the 
surface itself seems even more brilliantly co- 
loured : it is only by attentive observation that 
we can distinguish the edges and borders firom 
the colour of the figure itself. 

I 2 



Digitized by 



Google 



116 COLOUEED OBJECTS DISPLACED BY EEFBACTION. 

282. 

The yellow and red squares, on the other 
hand, are comparatively reduced by the hetero- 
geneous edges in this position of the figures, 
and their colours are, to a certain extent, vitiated. 
The blue edge in both is almost invisible. The 
violet border appears as a beautiful peach- 
blossom hue on the red, as a very pale colour of 
the same kind on the yellow ; both the lower 
edges are green ; dull on the red, vivid on the 
yellow ; the violet border is but faintly percep- 
tible under the red, but is more apparent under 
the yellow. 

283. 

Every inquirer should make it a point to be 
thoroughly acquainted with all the appearances 
here adduced, and not consider it irksome to 
follow out a single phenomenon through so 
many modifying circumstances* These expe- 
riments, it is true, may be multiplied to infinity 
by differently coloured figures, upon and be- 
tween differently coloured grounds. Under all 
such circumstances, however, it will be evident 
to every attentive observer that coloured squares 
only appear relatively altered, or elongated, or 
reduced by the prism, because an addition of 
homogeneous or heterogeneous edges produces 
an illusion. The inquirer will now be enabled 
to do away with this illusion if he has the 



Digitized by 



Google 



COLOUBED OBJECTS DISPLACED BY REFRACTION. 117 

patience to go through the experiments one after 
the other, always comparing the effects together, 
and satisfying himself of their correspondence. 

Experiments with coloured objects might 
have been contrived in various ways : why they 
have been exhibited precisely in the above mode, 
and with so much minuteness, will be seen here-» 
after. The phenomena, although formerly not 
unknown, were much misunderstood ; and it was 
necessary to investigate them thoroughly to 
render some portions of our intended historical 
view clearer. 

284. 

In conclusion, we will mention a contrivance 
by means of which our scientific readers may be 
enabled to see these appearances distinctly at 
one view, and even in their greatest splendour. 
Cut in a piece of pasteboard five perfectly simi-* 
lar square openings of about an inch, next each 
other, exactly in a horizontal line : behind these 
openings place five coloured glasses in the na« 
tural order, orange, yellow, green, blue, violet 
Let the series thus adjusted be fastened in an 
opening of the camera obscura, so that the 
bright sky may be seen through the squares, 
or that the sun may shine on them ; they 
will thus appear very powerfully coloured. Let 
the spectator now examine them through the 
prism, and observe the appearances, already 



Digitized by 



Google 



118 ACHROMATISM AND HYPERCHROMULTISM. 

fieuniliar by the foregoing experimentSi with 
coloured objects, namely, the partly assisting, 
partly neutralbing effects of the edges and bor^ 
ders, and the consequent apparent elongation or 
reduction of the coloured squares with reference 
to the horizontal line. The results witnessed by 
the observer in this case, entirely correspond 
with those in the cases before analysed ; we do 
not, therefore, go through them again in detail, 
especially as we shall find frequent occasions 
hereafter to return to the subject. — Note P» 



XIX. 

ACHROMATISM AND HYPERCHROMATISM. 
285. 

Formerly when much that is n^lar and con- 
stant in nature was considered as mere aber- 
ration and accident, the colours arising fixmi re- 
fraction were but little attended to, and were 
looked upon as an appearance attributable to 
particular local circumstances. 

286. 

But after it had been assumed that this ap- 
pearance of colour accompanies refraction at all 
times, it was natural that it should be considered 
as intimately and exclusively connected with 
that phenomenon ; the belief obtaining that the 



Digitized by 



Google 



ACHROMATISM AND HtPBROHKOMATISM. 1 19 

measure of the coloured appearance was in pro** 
portion to the measure of the refVaction, and 
that they must advance pari pMsu with each 
other. 

287, 

If, again, philosophers ascribed the pheno- 
menon of a stronger or weaker refraction, not 
indeed wholly, but in some degree, to the dif- 
ferent density of the medium^ (as purer atmo- 
spheric air, air charged with vapours, water, 
glass^ according to their increasing density, in- 
crease the so-called refraction, or displacement 
of the object ;) so they could hardly doubt that 
the appearance of colour must increase in the 
same proportion ; and hence took it for granted, 
in combining different mediums which were to 
counteract refraction, that as long as refraction 
existed, the appearance of colour must take 
place, and that as soon as the colour disappeared, 
the refraction also must cease. 

288. 

Afterwards it was, however, discovered that 
this relation which was assumed to correspond, 
was, in fact, dissimilar ; that two mediums can 
refract an object with equal power, and yet pro- 
duce very dissimilar coloured borders. 

289. 
It was found that, in addition to the physical 
principle to which refraction was ascribed, a 



Digitized by 



Google 



120 ACHROMATISM AND HTPEB€HBOMATISM. 

chemical one was also to be taken into the 
account. We propose to pursue this subject 
hereafter, in the chemical division of our in- 
quiry, and we shall have to describe the par- 
ticulars of this important discovery in our history 
of the doctrine of colours. What follows may 
suffice for the present 

290. 

In mediums of similar or nearly similar re- 
fracting power, we find the remarkable circum- 
stance that a greater and lesser appearance of 
colour can be produced by a chemical treat- 
ment; the greater efiect is owing, namely, to 
acids, the lesser to alkalis. If metallic oxydes 
are introduced into a common mass of glass, the 
coloured appearance through such glasses be- 
comes greatly increased without any perceptible 
change of refracting power. That the lesser 
effect, again, is produced by alkalis, may be 
easily supposed. 

291. 

Those kinds of glass which were first em- 
ployed after the discovery, are called flint and 
crown glass ; the first produces the stronger, 
the second the fainter appearance of colour. 

292. 

We shall make use of both these denomina- 
tions as technical terms in our present statement. 



Digitized by 



Google 



ACHROMATISIC AND HTPERCHROMATISM. 121 

and assume that the refractiye power of both is 
the same, but that flint-glass produces the 
coloured appearance more strongly by one-third 
than the crown-glass. The diagram (Plate 3, 
fig. 2,) may servcf in illustration. 

293. 

A black surface is here divided into com- 
partments for more convenient demonstration : 
let the spectator imagine five white squares be* 
tween the parallel lines a, h, and e, d. The 
square No. 1, is presented to the naked eye un- 
moved from its place. 

: 294. 

But let the square No. % seen through a 
crown-glass prism gy be supposed to be dis^ 
placed by refraction three compartments, ex- 
hibiting the coloured borders to a certain extent; 
again, let the square No. 3, seen through a flint 
glass prism A, in like manner be moved down- 
wards three compartments, when it will exhibit 
the coloured borders by about a third wider 
than No. 2. 

295. 

Again, let us suppose that the square No. 4, 
has, like No. 2, been moved downwards three 
compartments by a prism of crown-glass, and 
that then by an oppositely placed prism A, of 



Digitized by 



Google 



122 ACHROMATISM AND HTPEBCHBOMATIBM. 

flint-glass, it has been again raised to its fonaer 
situation, where it now stands. 

296. 

Here, it is true, the refraction is done away 
with by the opposition of the two ; but as the 
prism h, in displacing the square by refraction 
through three compartments, produces coloured 
borders wider by a third than those produced by 
the prism g-, so, notwithstanding the refraction 
is neutralised, there must be an excess of 
coloured border remaining. (The position of this 
colour, as usual, depends on the direction of the 
apparent motion (204) communicated to the 
square by the prism h, and, consequently^ it is 
the reverse of the appearance in the two squares 
2 and 3, which have been moved in an opposite 
direction.) This excess of colour we have called 
Hyperchromatism, and from this the achromatic 
state may be immediately arrived at 

297- 

For assuming that it was the square No. 6 
which was removed three compartments from 
its first supposed place, like No. % by a prism 
of crown-glass g, it would only be necessary to 
reduce the angle of a prism of flint-glass A, and 
to connect it, reversed, to the prism g^ in order 
to raise the square No. 5 two degrees or com- 
partments; by which means the Hyperchro- 



Digitized by 



Google 



ADVANTAGES OF SUBJECTITE EXPERIMENTS. 123 

Hiatism of the first case would cease, the figure 
would not quite return to its first position, and 
yet be already colourless. The prolonged lines 
of the united prisms, under No. 5, show that a 
single complete prism remains : again, we have 
only to suppose the lines curved, and an object-- 
glass presents itself. Such is the principle of 
the achromatic telescopes. 

298. 

For these experiments, a small prism com^ 
posed of three difi*erent prisms, as prepared in 
England, is extremely well adapted. It is to be 
hoped our own opticians will in future enable 
every friend of science to provide himself with 
this necessary instrument. 



XX. 

ADVANTAGES OF SUBJECTIVE EXPERIMENTS— TRANSITION 
TO THE OBJECTIVE. 

299. 

We have presented the appearances of colour 
as exhibited by refraction, first, by means of 
subjective experiments; and we have so far 
arrived at a definite result, that we have been 
enabled to deduce the phenomena in question 



Digitized by 



Google 



124 ADVANTAGES OF SUBJECTIYE BXPERIMENTS— 

from the doctrine of semi-transparent mediums 
and double images. 

300. 

In statements which have reference to nature, 
everything depends on ocular inspection^ and 
these experiments are the more satisfactory as 
they may be easily and conveniently made. 
Every amateur can procure his apparatus with- 
out much trouble or cost, and if he is a tolerable 
adept in pasteboard contrivances, he may even 
prepare a great part of his machinery himself. 
A few plain surfaces, on which black, white, 
grey, and coloured objects may be exhibited 
alternately on a light and dark ground, are all 
that is necessary. The spectator fixes them 
before him, examines the appearances at the 
edge of the figures conveniently, and as long as 
he pleases ; he retires to a greater distance, 
again approaches, and accurately observes the 
progressive states of the phenomena. 

301. 

Besides this, the appearances may be ob- 
served with sufficient exactness through small 
prisms, which need not be of the purest glass. 
The other desirable requisites in these glass in^ 
Btruments will, however, be pointed out in the 
section which treats of the apparatus.* 

* This deacriptioD of the apparatus was never given. 



Digitized by 



Google 



OBIBCTIVE EXPERIMENTS. 125 

302. 

A great advantage in these experiments, again, 
is^ that they can be made at any hour of the day 
in any room, whatever aspect it may have. We 
have no need to wait for sunshine, which in 
general is not very propitious to northern ob- 
servers. 

OBJECTIVE EXPERIMENTS. 
303. 

The objective experiments, on the contrary, 
necessarily require the sun-light which, even 
when it is to be had, may not always have the 
most desirable relation with the apparatus 
placed opposite to it. Sometimes the sun is 
too high, sometimes too low, and withal only a 
short time in the meridian of the best situated 
room. It changes its direction during the ob- 
servation,' the observer is forced to alter his own 
position and that of his apparatus, in conse- 
quence of which the experiments in many cases 
become uncertain. If the sun shines through 
the prism it exhibits all inequalities, lines, 
and bubbles in the glass, and thus the appear- 
ance is rendered confused, dim, and discoloured. 

304. 
Yet both kinds of experiments must be inves- 
tigated with equal accuracy. They appear to 



Digitized by 



Google 



120 OBJECTIVE EXPERIMENTS. 

be opposed to each other, and yet are always 
parallel. What one order of experiments exhi- 
bits the other exhibits likewise, and yet each 
has its peculiar capabilities, by means of which 
certain effects of nature are made known to us 
in more than one way. 

305. 

In the next place there are important pheno- 
mena which may be exhibited by the union of 
subjective and objective experiments. The 
latter experiments again have this advantage, 
that we can in most caBes represent them by 
diagrams, and present to view the component 
relations of the phenomena. In proceedmg^ 
therefore, to describe the objective experiments, 
we shall so arrange them that they may always 
correspond with the analogous subjective exam- 
ples ; for this reason, too, we annex to the num- 
ber of each paragraph the number of the former 
corresponding one. But we set out by ob- 
serving generally that the reader must consult 
the plates, that the scientific investigator must 
be familiar with the apparatus in order that the 
twin-phenomena in one mode or the other may 
be placed before them. 



Digitized by 



Google 



127 



XXI. 

BEFBACTION WITHOUT THE APPEARANCE OF COLOUR. 

306 (195, 196). 

That refraction may exhibit its effects without 
producing an appearance of colour, is not to be 
demonstrated so perfectly in objective as in sub- 
jective experiments. We have, it is true, un- 
limited spaces which we can look at through 
the prism, and thus convince ourselves that no 
colour appears where there is no boundary ; but 
we have no unlimited source of light which we 
can cause to act through the prism. Our light 
comes to us from circumscribed bodies ; and 
the sun, which chiefly produces our prismatic 
appearances, is itself only a small, circum- 
scribed, luminous object. 

307. 

We may, however, consider every larger open- 
ing through which the sun shines, every larger 
medium through which the sun-light is trans- 
mitted and made to deviate from its course, as 
so far unlimited that we can confine our atten- 
tion to the centre of the surface without con- 
sidering its boundaries. 

308 (197). 
If we place a large water-prism in the sun, a 



Digitized by 



Google 



128 CONDITIONS OF THE APPEARANCE OF COLOUR. 

large bright space is refracted upwards by it on 
the plane intended to receive the image> and the 
middle of this illumined space will be colourless. 
The same effect may be produced if we make 
the experiment with glass prisms having angles 
of few degrees : the appearance may be pro-> 
duced even through glass prisms, whose re- 
fracting angle is sixty degrees, provided we 
place the recipient surface near enough. 



XXII. 

CONDITIONS OF THE APPEARANCE OF COLOUR, 

309 (198). 

Although^ then, the illumined space before 
mentioned appears indeed refracted and moved 
from its place, but not coloured, yet on the hori- 
zontal edges of this space we observe a coloured 
appearance. That here again the colour is 
solely owing to the displacement of a circum- 
scribed object may require to be more fully 
proved. 

The luminous body which here acts is cir- 
cumscribed : the sun, while it shines and diffuses 
light, is still an insulated object. However 
small the opening in the lid of a camera obscura 
be made, still the whole image of the sun will 



Digitized by 



Google 



CONDITIONS OP THE APPBARANCE OF COLOUR. 129 

penetrate it The light which streams from all 
parts of the sun's disk* will cross itself in the 
smallest opening, and form the angle which 
corresponds with the sun's apparent diameter. 
On the outside we have a cone narrowing to the 
orifice ; within, this apex spreads again, produc* 
ing on an opposite surface a round image, which 
still increases in size in proportion to the dis- 
tance of the recipient surface from the apex. 
This image, together with all other objects of 
the external landscape, appears reversed on the 
white surface in question in a dark room. 

310. 
How little therefore we have here to do with 
single sun-rays, bundles or fasces of rays, cylin- 
ders of rays, pencils, or whatever else of the kind 
may be imagined, is strikingly evident. For the 
convenience of certain diagrams the sun-light 
may be assumed to arrive in parallel lines, but 
it is known that this is only a fiction ; a fiction 
quite allowable where the difference between 
the assumption and the true appearance is un- 
important; but we should take care not to suffer 
such a postulate to be equivalent to a fact, and 
proceed to further operations on such a fictitious 
basis. 

311. 
Let the aperture in the window-shutter be 
now enlarged at pleasure, let it be made round 



Digitized by 



Google 



130 CONDITIONS OF THE APPEARANCB OF COLOUR. 

or square, nay, let the whole shatter be opened, 
and let the sun shine into the room through the 
whole window ; the space which the sun illu- 
mines will always be larger according to the 
angle which its diameter makes ; and thus even 
the whole space illumined by the sun through 
the largest window is only the image of the sun 
pkis the size of the opening. We shall hereafter 
have occasion to return to this. 

312 (199). 

If we transmit the image of the sun through 
convex glasses we contract it towards the focus. 
In this case, according to the laws before ex- 
plainedy a yellow border and a yellow-red edge 
must appear when the spectrum is thrown on 
white paper. But as this experiment is dazzling 
and inconvenient, it may be made more agree- 
ably with the image of the full moon. On con- 
tracting this orb by means of a convex glass, the 
coloured edge appears in the greatest splendor ; 
for the moon transmits a mitigated light in the 
first instance, and can thus the more readily 
produce colour which to a certain extent accom- 
panies the subduing of light : at the same time 
the eye of the observer is only gently and agree- 
ably excited. 

313 (200). 

If we transmit a luminous image through con- 



Digitized by 



Google 



COm)ITION8 OF THB APPEARANCE OF COLOUR. 131 

cave glasses, it is dilated. Here the image ap- 
pears edged with blue. 

314. 

The two opposite appearances may be pro- 
duced by a convex glass, simultaneously or in 
succession; simultaneously by fastening an 
opaque disk in the centre of the convex glass, 
and then transmitting the sun*s image. In this 
case the luminous image and the black disk 
within it are both contracted, and, consequently, 
the opposite colours must appear. Again, we 
can present this contrast in succession by first 
contracting the luminous image towards the 
focus, and then suffering it to expand again 
beyond the focus, when it will immediately ex- 
hibit a blue edge. 

315 (201). 
Here too what was observed in the subjective 
experiments is again to be remarked, namely, 
that blue and yellow appear in and upon tl)^ 
white, and that both assume a reddish appear- 
ance in proportion as they mingle with the 
black. 

816 (202, 203). 

These elementary phenomena occur in all 
subsequent objective experiments^ as they con- 
stituted the groundwork of the subjective ones. 

k2 



Digitized by 



Google 



132 CONDITIONS OF THE APPEARANCE OF COLO0K. 

The process too which takes place is the same ; 
a light boundary is carried over a dark surface, 
a dark surface is carried over a light boundary. 
The edges must advance, and as it were push 
over each other in these experiments as in the 
former ones. 

317 (204). 

If we admit the sun*s image through a larger 
or smaller opening into the dark room, if we 
transmit it through a prism so placed that its 
refracting angle, as usual, is underneath ; the 
luminous image, instead of proceeding in a 
straight line to the floor, is refracted upwards 
on a vertical surface placed to receive it. This 
is the moment to take notice of the opposite 
modes in which the subjective and objective re- 
fractions of the object appear. 

318. 

If we look through a prism, held with its re- 
fracting angle underneath, at an object above 
us, the object is moved downwards; whereas a 
luminous image refracted through the same 
prism is moved upwards. This, which we here 
merely mention as a matter of fact for the sake 
of brevity, is easily explained by the laws of re- 
fraction and elevation. 



Digitized by 



Google 



CONDITIONS OF THE APPEARANCE OF COLOUR. 133 
319. 

The luminous object being moved from its 
place in this manner, the coloured borders ap- 
pear in the order; and according to the laws 
before explained. The violet border is always 
foremost, and thus in objective cases proceeds 
upwards, in subjective cases downwards. 

320 (205). 

The observer may convince himself in like 
manner of the mode in which the appearance of 
colour takes place in the diagonal direction 
when the displacement is effected by means of 
two prisms, as has been plainly enough shorwn 
in the subjective example ; for this experiment^ 
however, prisms should be procured of few de- 
grees, say about fifteen. 

321 (206, 207). 

That the colouring of the image takes place 
here too, according to the direction in which it 
moves, will be apparent if we make a square 
opening of moderate size in a shutter, and 
cause the luminous image to pass through a 
water-prism ; the spectrum being moved first in 
the horizontal and vertical directions, then dia- 
gonally, the coloured edges will change their 
position accordingly. 



Digitized by 



Google 



134 CONDITIONS OF THS AFP£ARANCS OF COLOUR. 

322 (208). 

Whence it is again evident that to produce 
colour the boundaries must be carried over each 
other, not merely move side by side. 



xxin. 

CONDITIONS OF THE INCRBASE OF COLOUR. 

323 (209). 

Here too an increased displacement of the ob- 
ject produces a greater appearance of colour. 

324 (210). 

This increased displacement occurs, 

1. By a more oblique direction of tlie im- 
pinging luminous object through mediums with 
parallel surfaces. 

2. By changing the parallel form for one 
more or less acute angled. 

8. By increased proportion of the medium, 
whether parallel or acute angled ; partly be- 
cause the object is by this means more power- 
fully displaced, partly because an effect depend* 
ing on the mere mass co-operates. 

4. By the distance of the recipient surface 
from the refracting medium so that the coloured 



Digitized by 



Google 



CONDITIONS OF THE INCRBA8B OF COLOUR. 1^5 

spectram emerging from the prism may be said 
to have a longer way to travel. 

5. When a chemical property produces its 
effects under all these circumstances: this we 
have already entered into more fully under the 
head of achromatism and hjrperchromatism. 

325 (211). 

The objective experiments have this advan- 
tage that the progressive states of the pheno- 
menon may be arrested and clearly represented 
by diagrams, which is not the case with the 
subjective experiments. 

326. 

We can observe the luminous image after it 
has emerged from the prism, step by step, and 
mark its increasing colour by receiving it on a 
plane at different distances, thus exhibiting 
before our eyes various sections of this cone, 
with an elliptical base : again, the phenomenon 
may at once be rendered beautifully visible 
throughout its whole course in the following 
manner : — Let a cloud of fine white dust be ex* 
cited along the line in which the image passes 
through the dark space ; the cloud is best pro- 
duced by fine, perfectly dry, hair-powder. The 
more or less coloured appearance will now be 
painted on the white atoms, and presented in 



Digitized by 



Google 



130 CONDITIONS OF THE INCREASE OF COLOUR. 

its whole length and breadth to the eye of the 
spectator. 

327. 

By this means we have prepared some dia- 
grams, which will be found among the plates. 
In these the appearance is exhibited from its 
first origin, and by these the spectator can 
clearly comprehend why the luminous image is 
so much more powerfully coloured through 
prisms than through parallel mediums. 

328 (212). 

At the two opposite outlines of the image an 
opposite appearance presents itself, beginning 
from an acute angle ;* the appearance spreads as 
it proceeds further in space, according to this 
angle. On one side, in the direction in which 
the luminous image is moved^ a violet border 
advances on the dark, a narrower blue edge re- 
mains next the outline of the image. On the 
opposite side a yellow border advances into the 
light of the image itself^ and a yellow-red edge 
remains at the outline. 

329 (213). 

Here, therefore, the movement of the dark 
against the light, of the light against the dark, 
may be clearly observed. 

♦ Plate iv. fig. 1. 



Digitized by 



Google 




Digitized by 



Google 



Digitized by 



Google 



CONDITIONS OF THE INCREA8B OF COLOUR. 137 

330 (214). 

The centre of a large object remains long un« 
coloured, especially with mediums of less den- 
sity and smaller angles ; but at last the oppo- 
site borders and edges touch each other, upon 
which a green appears in the centre of the lu- 
minous image. 

331 (215). 

Objective experiments have been usually 
made with the sun's image : an objective expe- 
riment with a dark object has hitherto scarcely 
been thought of. We have, however, prepared 
a convenient contrivance for this also. Let the 
large water-prism before alluded to be placed in 
the sun, and let a round pasteboard disk be 
fastened either inside or outside. The coloured 
appearance will again take place at the outline, 
beginning according to the usual law ; the edges 
will appear, they will spread in the same pro- 
portion, and when they meet, red will appear io 
the centre.^ An intercepting square may be 
added near the round disk, and placed in any 
direction ad libitum^ and the spectator can again 
convince himself of what has been before so 
often described. 

332 (216). 

If we take away these dark objects from the 

* Plate iv. fig. 2. 



Digitized by 



Google 



138 coNDrrioNs of thb incbbasb 01?* ooloub. 

prism, in which case, however, the glass is to be 
carefully cleaned, and hold a rod or a large 
pencil before the centre of the horizontal prism, 
we shall then accomplish the complete immixture 
of the violet border and the yellow-red edge, 
and see only the three colours, the external 
blue, and yellow, and the central red. 

333. 
If again we cut a long horizontal opening in 
the middle of a piece of pasteboard, fastened on 
the prism, and then cause the sun-light to pass 
through it, we shall accomplish the complete 
union of the yellow border with the blue edge 
upon the light, and only see yellow-red, green 
and violet. The details of this are further 
entered into in the description of the plates. 

334 (217). 
The prismatic appearance is thus by no 
means complete and final when the luminous 
image emerges from the prism. It is then only 
that we perceive its elements in contrast; for as 
it increases these contrasting elements unite, 
and are at last intimately joined. The section 
of this phenomenon arrested on a plane surface 
is different at every degree of distance from the 
prism ; so that the notion of an immutable series 
of colours, or of a pervading similar proportion 
between them, cannot be a question for a 
moment. 



Digitized by 



Google 



EXPLANATION OF THE FOBEQOINO PHENOMENA. 139 

XXIV. 

EXPLANATION OF THE FOREGOINQ PHENOMENA. 
335 (218). 

As we have already entered into this analysis 
circumstantially while treating of the subjective 
experiments, as all that was of force there is 
equally valid here, it will require no long de* 
tails in addition to show that the phenomena^ 
which are entirely parallel in the two cases, may 
also be traced precisely to the same sources. 

336 (219). 

That in objective experiments also we have 
to do with circumscribed images, has been al- 
ready demonstrated at large. The sun may 
shine through the smallest opening, yet the 
image of the whole disk penetrates beyond. 
The largest prism may be placed in the open 
sun-light, yet it is still the sun's image that is 
bounded by the edges of the refracting surfaces, 
and produces the accessory images of this bound- 
ary. We may fasten pasteboard, with many 
openings cut in it, before the water-prism, yet 
we still merely see multiplied images which, 
after having been moved from their place by 
refraction, exhibit coloured edges and borders, 
and in these mere accessory images. 



Digitized by 



Google 



140 eXPLANATIOK OF THE FOREGOING PHENOMENA. 

337 (235). 

In subjective experiments we have seen that 
objects strongly relieved from each other pro- 
duce a very lively appearance of colour, and 
this will be the case in objective experiments in 
a much more vivid and splendid degree. The 
sun's image is the most powerful brightness we 
know ; hence its accessory image will be ener- 
getic in proportion, and notwithstanding its 
really secondary dimmed and darkened charac- 
ter, must be still very brilliant. The colours 
thrown by the sun-light through the prism on 
any object, carry a powerful light with them, 
for they have the highest and most intense 
source of light, as it were, for their ground. 

338. 

That we are warranted in calling even these 
accessory images semi-transparent, thus de- 
ducing the appearances from the doctrine of 
the semi-transparent mediums, will be clear to 
every one who has followed us thus far, but par- 
ticularly to those who have supplied themselves 
with the necessary apparatus, so as to be en- 
abled at all times to witness the precision and 
vivacity with which semi-transparent mediums 
act 



Digitized by 



Google 



DECREASE OF THE APPEARANCE OF COLOUR. 141 

XXV- 

DECREASE OF THE APPEARANCE OF COLOUR. 

339 (243). 
If we could afford to be concise in the descrip- 
tion of the decreasing coloured appearance in 
subjective cases, we may here be permitted to 
proceed with still greater brevity while we refer 
to the former distinct statement. One circum- 
stance, only on account of its great importance, 
may be here recommended to the reader's espe- 
cial attention as a leading point of our whole 
thesis. 

340 (244, 247). 
The decline of the prismatic appearance 
must be preceded by its separation, by its reso- 
lution into its elements. At a due distance from 
the prism, the image of the sun being entirely 
coloured, the blue and yellow at length mix 
completely, and we see only yellow-red, green, 
and blue-red. If we bring the recipient surface 
nearer to the refracting medium, yellow and 
blue appear again, and we see the five colours 
with their gradations. At a still shorter dis- 
tance the yellow and blue separate from each 
other entirely, the green vanishes, and the 
image itself appears^ colourless, between the 
coloured edges and borders. The nearer we 
bring the recipient surface to the prism, the 



Digitized by 



Google 



142 OBEY OBJBCTS. 

narrower the edges and borders become, till at 
last, when in contact with the prism, they are 
reduced to nothing. 



XXVI. 

GREY OBJECTS. 



341 (218). 

We have exhibited grey objects as very im- 
portant to our inquiry in the subjective experi- 
ments. They show, by the faintness of the 
accessory images, that these same images are in 
all cases derived from the principal object. If 
we wish here, too, to carry on the objective ex- 
periments parallel with the others, we may con- 
veniently do this by placing a more or less dull 
ground glass before the opening through which 
the sun's image enters. By this means a sub- 
dued image would be produced, which on being 
refracted would exhibit much duller colours on 
the recipient plane than those immediately de- 
rived from the sun's disk ; and thus, even frt)m 
the intense sun-image, only a faint accessory 
image would appear, proportioned to the mi- 
tigation of the light by the glass. This expe- 
riment, it is trae^ will only again and again 
confirm what is already sufficiently familiar 
tons. 



Digitized by 



Google 



COLOURED OBJECTS. 143 

XXVII. 

COLOURED OBJECTS. 

342 (260). 
There are various modes of producing coloured 
images in objective experiments. In the first 
place, we can fix coloured glass before the open- 
ii^gf by which means a coloured image is at once 
produced ; secondly, we can fill the water-prism 
with coloured fluids; thirdly, we can cause the 
colours, already produced in their full vivacity 
by the prism, to pass through proportionate 
small openings in a tin plate, and thus prepare 
small circumscribed colours for a second opera- 
tion. This last mode is the most difficult ; for 
owing to the continual progress of the sun, the 
image cannot be arrested in any direction at 
will. The second method has also its incon- 
veniences, since not all coloured liquids can 
be prepared perfectly bright and clear. On 
these accounts the first is to be preferred, and 
deserves the more to be adopted because natural 
philosophers have hitherto chosen to consider 
the colours produced fit)m the sun-light through 
the prism, those produced through liquids and 
glasses, and those which are already fixed on 
paper or doth, as exhibiting efiects equally to 
be depended on, and equally available in de- 
monstration. 

343. 
As it is thus merely necessary that the image 



Digitized by 



Google 



144 COLOURED OBJECTS. 

should be coloured, so the large water-prism 
before alluded to affords us the best means of 
effecting this. A pasteboard screen may be 
contrived to slide before the large surfaces of 
the prism, through which^ in the first instance, 
the light passes uncoloured. In this screen 
openings of various forms may be cut, in order 
to produce different images, and consequently 
different accessory images. This being done, 
we need only fix coloured glasses before the 
openings, in order to observe what effect refrac- 
tion produces on coloured images in an objective 

344. 

A series of glasses may be prepared in a 
mode similar to that before described (284) ; 
these should be accurately contrived to slide in 
the grooves of the large water-prism. Let the 
sun then shine through them, and the coloured 
images refiticted upwards will appear bordered 
and edged, and will vary accordingly: for 
these borders and edges will be exhibited quite 
distinctly on some images, and on others will 
be mixed with the specific colour of the glass, 
which they will either enhance or neutralize. 
Every observer will be enabled to convince 
himself here again that we have only to do with 
the same simple phenomenon so circumstan- 
tially described subjectively and objectively. 



Digitized by 



Google 



ACHROMATISM AND HTPERCHROMATISM. 145 

XXVIII. 

ACHROlfATISM AND HTPERCHROlfATISM. 

345(285.290). 

It is possible to make the hyperchromatic and 
achromatic experiments objectively as well as 
subjectively. After what has been already 
stated, a short description of the method will 
suffice, especially as we take it for granted that 
the compound prism before mentioned is in the 
hands of the observer. 

346. 
Let the sun's image pass through an acute- 
angled prism of few degrees, prepared from 
crown-glass, so that the spectrum be refracted 
upwards on an opposite surface ; the edges will 
appear coloured, according to the constant law, 
namely, the violet and blue above and outside, 
the yellow and yellow-red below and within the 
image. As the refracting angle of this prism is 
undermost^ let another proportionate prism of 
flint-glass be placed against it, with its refracting 
angle uppermost. The sun's image will by this 
means be again moved to its place, where, owing 
to the excess of the colouring power of the 
prism of flint-glass, it will still appear a little 
coloured, and, in consequence of the direction 
in which it has been moved, the blue and violet 



Digitized by 



Google 



146 ACHBOMATI8M AND HTPERCHaOMATISM. 

will now appear underneath and outside, the 
yellow and yellow-red above and inside. 

347.'^ '• " "" '^' 
If the whole image be now moved a little up- 
wards by a proportionate prism of crown-glass, 
the h}rperchromati8m will disappear, the sun's 
image will be moved from its place, and yet 
will appear colourless. 

348. 

With an achromatic object-glass composed of 
three glasses, this experiment may be made 
step by step, if we do not mind taking out the 
glasses from their setting. The two convex 
glasses of crown-glass in contracting the sun's 
image towards the focus, the concave glass of 
flint-glass in dilating the image beyond it, Ex- 
hibit at the edges the usual colours. A convex 
glass united with a concave one exhibits the 
colours according to the law of the latter. If 
all three glasses are placed together, whether 
we contract the sun^s image towards the focus, 
or suffer, it to dilate beyond the focus, coloured' 
edges never appear, and the achromatic effect 
intended by the optician is, in this case, again 
attained. 

349. 

But as the crown-glass has always a greenish' 
tint, and as a tendency to this hue may be more 



Digitized by 



Google 



ACHROMATISM AND HTPEBCHROMATISM. 147 

decided in large and etrong otiject-glasse^, 
and under certain cirdumstances produce the 
compensatory; red, (whicli, howeTer^. in repeated 
eziyeriments with several, instrunients of thia 
kind, did not occur to us,) philosophers have 
resorted to the most extraordinaiy modes of 
explaining such a result ; and having been com- 
pelled, in support of their system, theoretically 
to prove the impossibility of achromatic tele- 
scopes, have felt a kind bf satisfaction in having 
some apparent ground for denying so great an 
improvement Of this, h(»iirever, we can omly 
treat circumstantially in our historical account 
of these discoveries. 



XXIX. 

COMBINATION OF SUBJECTIVE AND OBJECTIVE 
EXPERIMENTS. 

350. 

Having shown abave (318) that refraction, con- 
sidered objectively and subjectively, must ^ct in 
opposite directions, it will follow that if we com- 
bine the experiments, the effects will recipro- 
cally destroy each other. 

351. 

Let the sun's image be thrown upwards on a 

L 2 



Digitized by 



Google 



148 COMBINATION OF SUBJECTIVE 

vertical plane, through a horizontally-placed 
prism. If the prism is long enough to admit of 
the spectator also looking through it, he will see 
the image elevated by the objective refiraction 
again depressed, and in the same place in which 
it appeared without refraction. 

352. 

Here a remarkable case presents itself, but 
at the same time a natural result of a general 
law. For since, as often before stated, the ob- 
jective sun's image thrown on the vertical 
plane is not an ultimate or unchangeable state 
of the phenomenon, so in the above operation 
the image is not only depressed when seen 
through the prism, but its edges and borders 
are entirely robbed of their hues, and the 
spectrum is reduced to a colourless circular 
form. 

353. 

By employing two perfectly similar prisms 
placed next each other, for this experiment, we 
can transmit the sun's image through one, and 
look through the other. 

354. 

If the spectator advances nearer with the 
prism through which he looks, the image is 
again elevated, and by degrees becomes coloured 
according to the law of the first prism. If he 



Digitized by 



Google 



AND OBJECTIVE EXPERIMENTS. 149 

again retires till he has brought the image to the 
neutralized point, and then retires still farther 
away, the image, which had become round and 
colourless, moves still more downwards and be- 
comes coloured in the opposite sense, so that if 
we look through the prism and upon the re- 
fracted spectrum at the same time, we see the 
same image coloured according to subjective and 
objective laws. 

355. 

The modes in which this experiment may be 
varied are obvious. If the refracting angle of 
the prism, through which the sun's image was 
objectively elevated, is greater than that of the 
prism through which the observer looks, he 
must retire to a much greater distance, in order 
to depress the coloured image so low on the 
vertical plane that it shall appear colourless, 
and vice versd. 

356. 

It will be easily seen that we may exhibit 
achromatic and hyperchromatic effects in a 
similar manner, and we leave it to the amateur 
to follow out such researches more fully. Other 
complicated experiments in which prisms and 
lenses are employed together, others again, in 
which objective and subjective experiments are 
variously intermixed, we reserve for a future 



Digitized by 



Google 



150 TRANSITION. 

occasion, when it will be our object to trace such 
effects to :the simple phenomena with which we 
are now sufficiently familiar. 



xxx; 

TRANSITION. 



357. 

In looking back on the description and analysis 
of dioptrical colours, we do not repent either 
that we have treated them so circumstantially, 
or that we have taken them into consideration 
before the other physical colours, out of the 
order we ourselves laid down. Yet, before we 
quit this branch of our inquiry, it^may be as 
well to state the reasons that have weighed 
with us. ^ , . 

358. 
If some apology is necessary for having 
treated the theory of the dioptrical colours^ paiv 
ticularly those of the second class, so diffusely, 
we should observe, that the exposition of any 
branch of knowledge is to be considered partly 
with reference to the intrinsic importance of the 
subject, and partly with reference to the par- 
ticular necessities of the time in which the 



Digitized by 



Google 



TRANSITION. 151 

inquiry is undertaken. In our own case we 
were forced to keep both these considerations 
constantly in view. In the first place we 
had to state a mass of experiments with our 
consequent convictions ; next, . it was o^r 
especial aim to exhibit certain phenomena 
(known, it is true, but misunderstood^ and above 
all, exhibited in false connection*) in that na- 
tural and progressive development which is 
strictly and truly conformable to observatiQA ; 
in order that hereafter, in our polemical or his- 
torical investigations, we might be enabled to 
bring a complete preparatory analysis to bear 
on, and elucidate, oar general view. The details 
we have entered into were on this account 
unavoidable ; they may be considered as a re- 
luctant consequence of the occasion. Hereafter, 
when philosophers will look upon a simple 
principle as simple, a combined efiect as 
combined; when they will i^cknpw^edge the 
first elementary, and the second complicated 
statte, for what they are ; then, indeed, all this 
statement may be abridged to a narrower fipirm ; 
a labour which, should we ourselves not be able 
to accomplish it, we bequeath to the active, in- 
terest of contemporaries and posterity. 

. 359. 

With respect to the order of the chapters, it 
should (be remembered that natural phenomena. 



Digitized by 



Google 



J52 TRANSITION. 

which are even allied to each other, are not con- 
nected in any particular sequence or constant 
series ; their efficient causes act in a narrow 
circle, so that it is in some sort indifferent what 
phenomenon is first or last considered ; the main 
point is, that all should be as far as possible 
present to us, in order that we may embrace 
them at last from one point of view, partly ac- 
cording to their nature, partly according to 
generally received methods. 

360. 

Yet, in the present particular instance, it may 
be asserted that the dioptrical colours are justly 
placed at the head of the physical colours ; not 
only on account of their striking splendour and 
their importance in other respects, but because, 
in tracing these to their source, much was ne- 
cessarily entered into which will assist our sub-* 
sequent enquiries. 

361. 

For, hitherto, light has been considered as a 
kind of abstract principle, existing and acting 
independently ; to a certain extent self-modified, 
and on the slightest cause, producing colours 
out of itself To divert the votaries of physical 
science from this mode of viewing the subject ; 
to make them attentive to the fact, that in pris- 
matic and other appearai;ices we have not to do 



Digitized by 



Google 



TRANSITION. 153 

with light as an uncircumscribed and modify- 
ing principle, but as circumscribed and modi* 
fied ; that we have to do with a luminous image ; 
with images or circumscribed objects generally, 
whether light or dark : this was the purpose we 
had in view, and such is the problem to be solved. 

362. 

All that takes place in dioptrical cases, — 
especially those of the second class which are 
connected with the phenomena of refraction, — is 
now sufficiently familiar to us, and will serve 
as an introduction to what follows. 

363. 

Catoptrical appearances remind us of the 
physiological phenomena, but as we ascribe a 
more objective character to the former, we 
thought ourselves justified in classing them 
with the physical examples. It is of import* 
ance, however, to remember that here again it 
is not light, in an abstract sense, but a luminous 
image that we have to consider. 

364. 

In proceeding onwards to the paroptrical 
class, the reader, if duly acquainted with the 
foregoing facts, will be pleased to find himself 
once more in the region of circumscribed forms. 
The shadows of bodies, especially, as secondary 



Digitized by 



Google 



154 CATOPTRIC AL COLOURS. 

images, so exactly acx^mpanying the object, 
will serve greatly to elucidate analogous ap- 
pearances. 

365, 

We will not, however, anticipate these state- 
ments, but proceed as heretofore in what we 
consider the regular course. 



XXXl. 

CATOPTRTCAL COLOURS. 



366. 

Catoptrical GolouiB are such as appear in con- 
sequence of a mirror-like reflection. We as- 
sume, in the first pku^e, that the light itself as 
well OS the surface from which it is reflecte,d» is 
perfectly colouriessi In this sense the appear- 
ances in question come under the head of phyi 
sical colours. They arise in consequence of 
reflection, as we found the dioptrical colours of 
the second class appear by means of refiraction. 
Without further general definitions^ we turn our 
attention at once to particular cases, and to thd 
conditions which are essential to the exhibition 
of these phenomena. 



Digitized by 



Google 



CATOPTRICAL COLOURS. 165 

367. 

If we unroll a coil of bright steel-wire, and 
after suffering it to spring confusedly together 
again, place it at a window in the light, we shall 
see the prominent parts of the circles and con- 
volutions illumined, but neither ifesplendent 
nor iridescent But if the. sun shines on the 
wire, this light will be condensed into a point, 
and we perceive a small resplendent image of 
tl^e sun, which, when seen near, exhibits no 
colour. On retiring a little, however^ and fixing 
the, eyes on this refulgent appearance, we dis- 
cern several small mirrored suns, coloured in the 
most varied manner ; and although the impres- 
sion is that green and red predominate, yet, on 
a more accurate iospection, we find that the 
other colours are also present 

368. , 

If we fake' ati ej^e-glass, aiid examine the Ap- 
pearance through it, we find the colours have 
vanished, as well as the radiating Splendour in 
which they Ifrere been, ahd we perceive only th^ 
small luminous points, the repeated images of 
the sun.' We thus find that the impression is 
subjective in its nature, and that the appear^ 
ance is allied to those which we have adverted 
to under the name of radiating halps (100). 



Digitized by 



Google 



156 CATOPTEICAL COLOURS. 

369. 

We can, however, exhibit this phenomenon 
objectively. Let a piece of white paper be fast- 
ened beneath a small aperture in the lid of a 
camera-obscura, and when the sun shines 
through this aperture, let the confusedly-rolled 
steel«wire be held in the light, so that it be op- 
posite to the paper. The sun-light will impinge 
on and in the circles of the wire, and will not, 
as in the concentrating lens of the eye, display 
itself in a point ; but, as the paper can receive 
the reflection of the light in every part of its 
surface will be seen in hair-like lines, which are 
also iridescent. 

370. 

This experiment is purely catoptrical ; for as 
we cannot imagine that the light penetrates the 
surface of the steel, and thus undergoes a 
change, we are soon convinced that we have 
here a mere reflection which, in its subjective 
character, is connected with the theory of faintly 
acting lights, and the after-image of dazzling 
lights, and as far as it can be considered ob- 
jective, announces even in the minutest appear- 
ances, a real efiect, independent of the action 
and reaction of the eye. 

371. 
We have seen that to produce these efiects 



Digitized by 



Google 



CATOPTRICAL COLOURS. 157 

not merely light but a powerful light is neces- 
sary; that this powerful light again is not an 
abstract and general quality, but a circumscribed 
light, a luminous image. We can convince our- 
selves still further of this by analogous cases. 

372. 

A polished surface of silver placed in the sun 
reflects a dazzling light, but in this case no 
colour is seen. If, however, we slightly scratch 
the surface, an iridescent appearance, in which 
green and red are conspicuous, will be exhibited 
at a certain angle. In chased and carved 
metals the effect is striking : yet it may be re- 
marked throughout that, in order to its appear- 
ance, some form, some alternation of light and 
dark must co-operate with the reflection ; thus 
a window-bar, the stem of a tree, an accident- 
ally or purposely interposed object produces a 
perceptible efiect. This appearance, too, may 
be exhibited objectively in the camera-obscura. 

373. 

If we cause a polished plated surface to be so 
acted on by aqua fortis that the copper within is 
touched, and the surface itself thus rendered 
rough, and if the sun's image be then reflected 
from it, the splendour will be reverberated from 
every minutest prominence^ and the surface will 
appear iridescent. So, if we hold a sheet of 



Digitized by 



Google 



158 CATOPTRICAL COLOITRS. 

black unglazed paper in the sun, and look at it. 
attentively, it will be seen to glisten in its mi- 
nutest points with the most vivid colours* 

874. 

All these examples are referable to the same 
conditions. In the first case the luminous 
image is Teflected- from a thin line ; in the 
second probiably from sh^urp edges; in the third 
from very small points. In all a very powerful- 
and circumddribed light is requisite. For all 
these appearances of colour again it is necessary 
that the eye should be at a due distance from- 
the reflecting points. 

875. 
If these observations are made with the mi^ 
ch>scope, the appeai*ance will be greatly in- 
creased in force and splendour^ for we then see 
tiie snJalleM portion of the surfaces, lit by the 
suh^ glittering in these/colours of reflection, 
which, allied to the hues of refraction, now 
attain their highest degree of brilliancy. In 
such cases We may observe a vermiform iri- 
descence on the stirfabe of organic bodies, the 
further description of which will be given here? 
after. ■ ■ > ■ 

376. 
Lastly, the colours which are chiefly exhi*' 



Digitized by 



Google 



CATOPTBICAL OOLOiniS. 159 

bited in reflection are red and green, whence 
we may infer that the linear appearance espe- 
cially conaifits of a thin line of red, bounded by 
blue on one side and yellow on the other, if 
these triple lines approach very near together, 
the intermediate space must appear green; a 
phenomenon which will often occur to us as we 
proceed. 

377. 

We frequently meet with these colours in 
nature. The colours of the spider's web oatght 
be considereid exactly of the same class with 
those reflected' from the steel wire, except that 
the non-translucent quality of the former is not 
so certain as in the case of steel ; on which ac- 
count some have been inclined' to class the 
colours of the spider's web with the phenomena 
of refraction. • 

. 378, . . , . .. . 
In mother-of-pearl we perceive infinitely fine 
organic fibres and lamellae in juxta-position, 
from which, as from the scratched silver before 
alluded to, varied colours, but especially red and 
green, may arise. . ; > > 

379. 
The changing colours of the plumage of birds 
may idso be mentioned here, although in all or* 



Digitized by 



Google 



160 CATOPTRICAL COLOURS. 

ganic instances a chemical principle and an 
adaptation of the colour to the structure nday be 
assumed ; considerations to which we shall re- 
turn in treating of chemical colours. 

380. 

That the appearances of objective halos also 
approximate catoptrical phenomena will be 
readily admitted, while we again do not deny 
that refraction as well may here come into 
the account For the present we' restrict our- 
selves to one or two observations ; hereafter we 
may be enabled to make a fuller application of 
general principles to particular examples. 

381. 

We first call to mind the yellow and red 
circles produced on a white or grey wall by a 
light placed near it (88). Light when reflected 
appears subdued, and a subdued light excites 
tiie impression of yellow, and subsequently of 
red. 

382. 

Let the wall be illumined by a candle placed 
quite close to it. The farther the light is dif- 
fused the fainter it becomes ; but it is still the 
effect of the flame, the continuation of its 
action, the dilated effect of its image. We 
might, therefore, very fairly call these circles 



Digitized by 



Google 



CATOPTRIC AL COLOURS. 161 

reiterated images, because they constitute the 
successive boundaries of the action of the light, 
and yet at the same time only present an ex- 
tended image of the flame. 

383. 

If the sky is white and luminous round the 
sun owing to the atmosphere being filled with 
light vapours; if mists or clouds pass be- 
fore the moon, the reflection of the disk mir- 
rors itself in them ; the halos we then perceive 
are single or double, smaller or greater, some- 
times very large, often colourless, sometimes 
coloured. 

384. 

I witnessed a very beautiful halo round the 
moon the 15th of November, 1799, when the 
barometer stood high ; the sky was cloudy and 
vapoury. The halo was completely coloured, 
and the circles were concentric round the light 
as in subjective halos. That this halo was ob- 
jective I was presently convinced by covering 
the moon's disk, when the same circles were 
nevertheless perfectly visible. 

385, 

The difierent extent of the halos appears to 
have a relation with the proximity or distance 
of the vapour from the eye of the observer. 

M 



Digitized by 



Google 



162 CATOPTRICAL COLOURS. 

386. 

As window-panes lightly breathed upon in- 
crease the brilliancy of subjective halos, and in 
some degree give them an objective character, 
80, perhaps, with a simple contrivance in winter, 
during a quickly freezing temperature, a more 
exact definition of this might be arrived at. 

387. 

How much reason we have in^ considering 
these circles to insist on the image and its 
efiects, is apparent in the phenomenon of the 
so-called double suns. Similar double images 
always occur in certain points of halos and 
circles, and only present in a circumscribed 
form what takes place in a more general way in 
the whole circle. All this will be more conve- 
niently treated in connexion with the appear- 
ance of the rainbow. — Note Q. 

388. 

In conclusion it is only necessary to point out 
the affinity between the catoptrical and parop^ 
tical colours. 

We call those paroptical colours which ap- 
pear when the light passes by the edge of an 
opaque colourless body. How nearly these are 
allied to the dioptrical colours of the second 
class will be easily seen by those who are con- 
vinced with us that the colours of refraction 



Digitized by 



Google 



CATOPTBICAI. COLOUBS. 108 

take place only at the edges of objects. The 
affinity again between the catoptricai and par- 
optical colours will be evident in the following 
chapt^. 



XXXII. 



PABOPTICAL COLOURS. 
389. 

The paroptical colours have been hitherto called 
peri-optical, because a peculiar effect of light 
was supposed to take place as it were round the 
object, and was ascribed to a certain flexibility 
of the light to and from the object. 

390. 

These colours again may be divided into sub- 
jective and objective, because they appear 
partly without us, as it were, painted on sur- 
faces, and partly within us, immediately on the 
Tetina. In this chapter we shall find it more to 
our purpose to take the objective cases first, 
since the subjective are so closely connected 
with other appearances already known to us, 
that it is hardly possible to separate them. 

391. 

The paroptical colours then are so called be- 

M 2 



Digitized by 



Google 



164 PAROPTICAL COLOURS. 

cause the. light must pass by au outline or edge 
to produce them. They do not, however, always 
appear in this case ; to produce the eflTect very 
particular conditions are necessary besides. 

392. 

It is also to be observed that in this instance 
again light does not act as an abstract diiSusion 
(361), the sun shines towards an edge. The 
volume of light poured from the sun-image 
passes by the edge of a substance, and occasions 
shadows. Within these shadows we shall pre^^ 
sently find colours appear. 

393. 

But, above all, we should make the experi* 
ments and observations that bear upon our pre- 
sent inquiry in the fullest light. We, there- 
fore, place the observer in the open air before 
we conduct him to the limits of a dark room. 

394. 

A person walking in sun-shine in a garden, or 
on any level path, may observe that his shadow 
only appears sharply defined next the foot on 
which he rests ; farther from this point, espe- 
cially round the head, it melts away into the 
bright ground. For as the sun-light proceeds 
not only from the middle of the sun, but also 
acts cross-wise from the two extremes of every 



Digitized by 



Google 



PAROPTICAL COLOURS. 165 

diameter, aa objective parallax takes place 
which produces a half-shadow on both sides of 
the objects 

395. 

If the person walking raises and spreads his 
hand, he distinctly sees in the shadow of each 
finger the diverging separation of the two half- 
shadows outwards, and the diminution of the 
principal shadow inwards, both being efiects of 
the cross action of the light. 

396. 

This experiment may be repeated and varied 
before a smooth wall, with rods of different 
thicknesses, and again with balls; we shall 
always find that the farther the object is re- 
moved from the surface of the wall, the more 
the weak double shadow spreads, and the more 
the forcible main shadow diminishes, till at last 
the main shadow appears quite effaced, and 
even the double shadows become so faint, that 
they almost disappear ; at a still greater dis- 
tance they are, in fact, imperceptible. 

397. 

That this is caused by the cross-action of the 
light we may easily convince ourselves ; for the 
shadow of a pointed object plainly exhibits two 
points. We must thus never lose sight of the 



Digitized by 



Google 



160 PAROPTICAL COLOURS. 

fact that in this case the whole sun-image acts» 
produces shadows, changes them to double 
shadows, and finally obliterates them. 

398. 

Instead of solid bodies let us now take open- 
ings cut of various given sizes next each other, 
and let the sun shine through them on a plane 
surface at some little distance ; we shall find 
that the bright image produced by the sun on 
the surface, is larger than the opening ; this is 
because one edge of the sun shines towards the 
opposite edge of the opening, while the other 
edge of the disk is excluded on that side. 
Hence the bright image is more weakly lighted 
towards the edges. 

399. 
If we take square openings of any size we 
please, we shall find that the bright image on a 
surface nine feet from the opening, is on every 
side about an inch larger than the opening ; 
thus nearly corresponding with the angle of the 
apparent diameter of the sun. 

400. 

That the brightness should gradually diminish 
towards the edges of the image is quite natural, 
for at last only a minimum of the light can act 
cross-wise from the sun's circumference through 
the edge of the aperture. 



Digitized by 



Google 



PABOPTICAL COLOURS. 167 

401. 

Thus we here again see how much reason we 
have in actual observation to guard against the 
assumption of parallel rays, bundles and fasces 
of rays, and the like hypothetical notions. 

402. 

We might rather consider the splendour of 
the sun, or of any light, as an infinite specular 
multiplication of the circumscribed luminous 
image, whence it may be explained that all 
square openings through which the sun shines, 
at certain distances, according as the apertures 
are greater or smaller, must give a round image 
of light. 

403. 

The above experiments may be repeated 
through openings of various shapes and sizes, 
and the same effect will always take place at 
proportionate distances. In all these cases, how- 
ever, we may still observe that in a full light 
and while the sun merely shines past an edge, 
no colour is apparent. 

404. 

We therefore proceed to experiments with a 
subdued light, which is essential to the appear- 
ance of colour. Let a small opening be made in 
the window-shutter of a dark room; let the 



Digitized by 



Google 



168 PAROPTICAL COLOURS. 

crossing sun-light which enters^ be received on 
a surface of white paper> and we shall find that 
the smaller the opening is» the dimmer the light 
image will be. This is quite obvious, because 
the paper does not receive light from the whole 
sun, but partially from single points of its disk. 

405. 

If we look attentively at this dim image of 
the sun, we find it still dimmer towards the out- 
lines where a yellow border is perceptible. The 
colour is still more apparent if a vapour or a 
transparent cloud passes before the sun, thus 
subduing and dimming its brightness. The 
halo on the wall, the efiect of the decreasing 
brightness of a light placed near it, is here 
forced on our recollection. (88.) 

406. 

If we examine the image more accurately, we 
perceive that this yellow border is not the only 
appearance of colour; we can see, besides, a 
bluish circle, if not even a halo-like repetition 
of the coloured border. If the room is quite 
dark, we discern ^hat the sky next the sun also 
has its effect : we see the blue sky, nay, even 
the whole landscape, on the paper, and are thus 
again convinced that as far as regards the 
sun, we have here only to do with a luminous 
image. 



Digitized by 



Google 



PAROPTICAL COLOURS, 169 

407. 

If \?e take a somewhat larger square opening, 
so large that the image of the sun shining 
through it does not immediately become round, 
we may distinctly observe the half-shadows of 
every edge or side, the junction of these in the 
corners, ajid their colours ; just as in the above- 
mentioned appearance with the round opening. 

408. 

We have now subdued a parallactic light 
by causing it to shine through small apertures, 
but we have not taken from it its parallactic 
character; so that it can produce double shadows 
of bodies, although with diminished power. 
These double shadows which we have hitherto 
been describing, follow each other in light and 
dark, coloured and colourless circles, and pro- 
duce repeated, nay, almost innumerable halos. 
These effects have been often represented in 
drawings and engravings. By placing needles, 
hairs, and other small bodies, in the subdued 
light, the numerous halo-like double shadows 
may be increased; thus observed, they have 
been ascribed to an alternating flexile action 
of the light, and the same assumption has been 
employed to explain the obliteration of the 
central shadow, and the appearance of a light 
in the place of the dark. 



Digitized by 



Google 



170 PAROPTICAL COLOURS. 

409. 

For ourselves, we maintain that these again 
are parallactic double shadows^ which appear 
edged with coloured borders and halos. 

410. 

After having seen and investigated the fore- 
going phenomena, we can proceed to the ex- 
periments with knife-blades,* exhibiting effects 
which may be referred to the contact and paral- 
lactic mutual intersection of the half-shadows 
and halos already familiar to us. 

411. 

Lastly, the observer may follow out the ex- 
periments with hairs, needles, and wires, in the 
half-light produced as before described by the 
sun, as well as in that derived from the blue 
sky, and indicated on the white paper. He will 
thus make himself still better acquainted with 
the true nature of this phenomenon. 

412. 

But since in these experiments everything 
depends on our being persuaded of the paral- 
lactic action of the light, we can make this 
more evident by means of two sources of light, 
the two shadows from which intersect each 
other, and may be altogether separated. By 
day this may be contrived with two small 

• Sec Newton's Optics, book iii. 



Digitized by 



Google 



PABOPTICAL COLOURS. 171 

openings in a window-shutter; by night, with 
two candies. There are even accidental effects 
in interiors, on opening and closing shutters^ by 
means of which we can better observe these ap* 
pearances than with the most careful apparatus. 
But still, all and each of these may be reduced 
to experiment by preparing a box which the 
observer can look into from above, and gradually 
diminishing the openings after having caused a 
double light to shine in. In this case, as might 
be expected, the coloured shadow, considered 
under the physiological colours, appears very 
easily. 

413. 

It is necessary to remember, generally, what 
has been before stated with regard to the nature 
of double shadows, half-lights, and the like. 
Experiments also should especially be made 
with different shades of grey placed next each 
other, where every stripe will appear light by a 
darker, and dark by a lighter stripe next it. If 
at night, with three or more lights, we produce 
shadows which cross each other successively, 
we can observe this phenomenon very distinctly, 
and we shall be convinced that the physiological 
case before more fully treated, here comes into 
the account (38). 

414. 

To what extent the appearances that accom-* 



Digitized by 



Google 



172 PAROPTICAL COLOURS. 

pany the paroptical colours, may be derived 
from the doctrine of subdued lights, from half- 
shadows, and from the physiological disposition 
of the retina, or whether we shall be forced to 
take refuge in certain intrinsic qualities of light, 
as has hitherto been done, time may teach. 
Suffice it here to have pointed out the con- 
ditions under which the paroptical colours ap* 
pear, and we may hope that our allusion to 
their connexion with the facts before adduced 
by us will not remain unnoticed by the ob- 
servers of nature. 

415. 

The affinity of the paroptical colours with the 
dioptrical of the second class will also be readily 
seen and followed up by every reflecting inves- 
tigator. Here, as in those instances, we have 
to do with edges or boundaries; here, as in 
those instances, with a light, which appears at 
the outline. How natural, therefore, it is to 
conclude that the paroptical effects may be 
heightened, strengthened, and enriched by the 
dioptrical. Since, however, the luminous image 
actually shines through the medium, we can 
here only have to do with objective cases of re- 
fraction : it is these which are strictly allied to 
the paroptical cases. The subjective cases of 
refraction, where we see objects through the 
medium, are quite distinct from the paroptical. 



Digitized by 



Google 



PAROPTICAL COLOURS. 173 

We have already recommended them on ac- 
count of their clearness and simplicity. 

416. 

The connexion between the paroptical colours 
and the catoptrical may be already inferred 
from what has been said : for as the catoptrical 
colours only appear on scratches, points, steel- 
wire, and delicate threads, so it is nearly the 
same case as if the light shone past an edge. 
The light must always be reflected from an 
edge in order to produce colour. Here again, 
as before pointed out, the partial action of the 
luminous image and the subduing of the light 
are both to be taken into the account. 

417. 

We add but few observations on the subjective 
paroptical colours, because these may be classed 
partly with the physiological colours, partly 
with the dioptrical of the second order. The 
greater part hardly seem to belong here, but, 
when attentively considered, they still difiuse a 
satisfactory light over the whole doctrine^ and 
establish its connexion. 

418. 

If we hold a ruler before the eyes so that the 
flame of a light just appears above it, we see 
the ruler as it were indented and notched at the 



Digitized by 



Google 



174 PAROPTICAL C0L0TTB8. 

place where the light appears. This seems de- 
ducible from the expansive power of light acting 
on the retina (18). 

419. 

The same phenomenon on a large scale is ex* 
hibited at sun-rise ; for when the orb appears 
distinctly, but not too powerfully, so that we can 
still look at it, it always makes a sharp indent- 
ation in the horizon. 

420. 

If, when the sky is grey, we approach a win* 
dow, so that the dark cross of the window-bars 
be relieved on the sky ; if after fixing the eyes 
on the horizontal bar we bend the head a little 
forward ; on half closing the eyes as we look up, 
we shall presently perceive a bright yellow-red 
border under the bar, and a bright light-blue 
one above it. The duller and more monotonous 
the grey of the sky, the more dusky the room, 
and, consequently, the more previously unex- 
cited the eye, the livelier the appearance will 
be ; but it may be seen by an attentive observer 
even in bright daylight. 

421. 

If we move the head backwards while half 
closing the eyes^ so that the horizontal bar be 
seen below^ the phenomenon will appear re- 



Digitized by 



Google 



PAKOPTICAL COLOURS. 175 

versed. The upper edge will appear yellow, 
the under edge blue. 

422. 

Such observations are best made in a dark 
room. If white paper is spread before the 
opening where the solar microscope is com- 
monly fastened, the lower edge of the circle 
will appear blue, the upper yellow, even while 
the eyes are quite open, or only by half-closing 
them so far that a halo no longer appears round 
the white. If the head is moved backwards the 
colours are reversed. 

423. 

These phenomena seem to prove that the hu" 
incurs of the eye are in fact only really achro- 
matic in the centre where vision takes place, 
but that towards the circumference, and in un- 
usual motions of the eyes, as in looking hori- 
zontally when the head is bent backwards or 
forwards, a chromatic tendency remains, espe- 
cially when distinctly relieved objects are thus 
looked at. Hence such phenomena may be 
considered as allied to the dioptrical colours of 
the second class. 

424. 

Similar colours appear if we look on black 
and white objects, through a pin-hole in a card» 



Digitized by 



Google 



176 PAROPTICAL COLOURS. 

Instead of a white object we may take the mi-« 
nute light aperture in the tin plate of a camera 
obscura, as prepared for paroptical experi- 
ments. 

425. 

If we look through a tube, the farther end of 
which is contracted or variously indented, the 
same colours appear. 

426. 

The following phenomena appear to me to be 
more nearly allied to the paroptical appear- 
ances. If we hold up a needle near the eye, 
the point appears double. A particularly re- 
markable effect again is produced if we look 
towards a grey sky through the blades of knives 
prepared for paroptical experiments. We seem 
to look through a gauze ; a multitude of threads 
appear to the eye ; these are in fact only the 
reiterated images of the sharp edges, each of 
which is successively modified by the next, or 
perhaps modified in a parallactic sense by the 
oppositely acting one, the whole mass being 
thus changed to a thread-like appearance. 

427. 

Lastly, it is to be remarked that if we look 
through the blades towards a minute light in 



Digitized by 



Google 



PAROPTICAL COLOURS. 177 

the window-shutter, coloured stripes and halos 
appear on the retina as on the paper. 

428. 

The present chapter may be here terminated, 
the less reluctantly, as a friend has undertaken 
to investigate this subject by further experi- 
ments. In our recapitulation, in the descrip* 
tion of the plates and apparatus, we hope here« 
after to give an account of his observations.* 



XXXIIl. 

EPOPTICAL COLOURS. 



429. 

We have hitherto had to do with colours which 
appear with vivacity, but which immediately 
vanish again when certain conditions cease. 
We have now to become acquainted with others, 
which it is true are still to be considered as 
transient, but which, under certain circum- 
stances, become so fixed that, even after the 
conditions which first occasioned their appear- 
ance cease, they still remain, and thus con- 

* The observationB here alluded to never appeared. 

N 



Digitized by 



Google 



178 EPOPTICAL COLOURS. 

stitute the link between the physical and the 
chemical colours. 

430. 

They appear from various causes on the sur- 
face of a colourless body, originally, without 
communication, die or immersion Oot^i^) ; and 
we now proceed to trace them, from their faint- 
est indication to their most permanent state, 
through the different conditions of their appear- 
ance, which for easier survey we here at once 
summarily state. 

431. 

First condition. — ^The contact of two smooth 
surfaces of hard transparent bodies. 

First case : if masses or plates of glass, or if 
lenses are pressed against each other. 

Second case : if a crack takes place in a 
solid mass of glass, chrystal, or ice. 

Third case : if lamellae of transparent stones 
become separated. 

Second condition. — ^If a surface of glass or a 
polished stone is breathed upon. 

Third condition. — ^The combination of the 
two last; firsts breathing on the glass, then 
placing another plate of glass upon it, thus ex- 
citing the colours by pressure ; then removing 
the upper glass, upon which the colours begin 
to fade and vanish with the breath. 



Digitized by 



Got)gle 



BPOPTICAL COLOURS. 179 

Fourth condition. — Bubbles of various liquids, 
soap, chocolate, beer, wine, fine glass bubbles. 

Fifth condition. — Very fine pellicles and la- 
mellae, produced by the decomposition of mine- 
rals and metals. The pellicles of lime, the sur- 
face of stagnant water, especially if impregnated 
with iron, and again pellicles of oil on water, 
especially of varnish on aqua fortis. 

Sixth condition. — If metals are heated ; the 
operation of imparting tints to steel and other 
metals. 

Seventh condition. — If the surface of glass is 
beginning to decompose. 

432. 

First condition, first case. If two convex 
glasses, or a convex and plane glass, or, best of 
all, a convex and concave glass come in contact, 
concentric coloured circles appear. The pheno- 
inenon exhibits itself immediately on the slight- 
est pressure, and may then be gradually carried 
through various successive states. We will de- 
scribe the complete appearance at once, as we 
shall then be better enabled to follow the differ- 
ent states through which it passes. 

433. 

The centre is colourless; where the glasses 
are, so to speak, united in one by the strongest 
pressure, a dark grey point appears with a silver 

n2 



Digitized by 



Google 



180 EPOPTICAL COLOURS. 

white space round it : then follow, in decreasing 
distances, various insulated rings, all consisting 
of three colours, which are in immediate con- 
tact with each other. Each of these rings, of 
which perhaps three or four might be counted, 
is yellow on the inner side, blue on the outer, 
and red in the centre. Between two rings there 
appears a silver white interval. The rings 
which are farthest from the centre are always 
nearer together : they are composed of red and 
green without a perceptible white space be- 
tween them. 

434. 
We will now observe the appearances in their 
gradual formation, beginning from the slightest 
pressure. 

435. 

On the slightest pressure the centre itself ap- 
pears of a green colour. Then follow as far as 
the concentric circles extend, red and green 
rings. They are wide, accordingly, and no trace 
of a silver white space is to be seen between 
them. The green is produced by the blue of an 
imperfectly developed circle, mixing with the 
yellow of the first circle. All the remaining 
circles are, in this slight contact, broad ; their 
yellow and blue edges mix together, thus pro- 
ducing a beautiful green. The red, however, of 



Digitized by 



Google 



EPOPTICAL COLOURS. 181 

each circle, remains pure and untouched ; hence 
the whole series is composed of these two 
colours. 

436. 

A somewhat stronger pressure separates the 
first cu*cle by a slight interval from the imper- 
fectly developed one : it is thus detached, 
and may be said to appear in a complete state. 
The centre is now a blue point ; for the yellow 
of the first circle is now separated from this 
central point by a silver white space. From the 
centre of the blue a red appears, which is thus, 
in all cases, bounded on the outside by its blue 
edge. The second and. third rings from the 
centre are quite detached. Where deviations 
from this order present themselves, the observer 
will be enabled to account for them, from what 
has been or remains to be stated. 

437. 

On a stronger pressure the centre becomes 
yellow ; this yellow is surrounded by a red and 
blue edge : at last, the yellow also retires from 
the centre ; the innermost circle is formed and 
is bounded with, yellow. The whole centre itself 
now appears silver white, till at last, on the 
strongest pressure, the dark point appears, and 
the phenomenon, as described at first, is com- 
plete. 



Digitized by 



Google 



182 EPOPTICAL COLOURS. 

438. 

The relative size of the concentric circles and 
their intervals depends on the form of the 
glasses ^hich are pressed together. 

439. 

We remarked above, that the coloured centre 
is, in fact, an undeveloped circle. It is, how- 
ever, often found, on the slightest pressure, that 
several undeveloped circles exist there, as it 
were, in the germ ; these can be successively 
developed before the eye of the observer. 

440. 

The regularity of these rings is owing to the 
form of the convex glasses, and the diameter of 
the coloured appearance depends on the greater 
or lesser section of a circle on which a lens is 
polished. We easily conclude from this, that 
by pressing plane glasses together, irregular 
appearances only will be produced ; the colours, 
in fact, undulate like watered silks, and spread 
from the point of pressure in all directions. Yet, 
the phenomenon as thus exhibited is much more 
splendid than in the former instance, and cannot 
fail to strike every spectator. If we make the 
experiment in this mode, we shall distinctly see, 
as in the other case, that, on a slight pressure, 
the green and red waves appear ; on a stronger, 
stripes of blue, red, and yellow, become de- 



Digitized by 



Google 



EPOPTICAL COLOT7B8. 183 

tached. At first, the outer sides of these stripes 
touch ; on increased pressure they are separated 
by a silver white space. 

441. 

Before we proceed to a further description of 
this phenomenon, we may point out the most 
convenient mode of exhibiting it. Place a large 
convex glass on a table near the window ; upon 
this glass lay a plate of well-polished mirror- 
glass, about the size of a playing-card, and the 
mere weight of the plate will press sufficiently 
to produce one or other of the phenomena above 
described. So, also, by the diflferent weight of 
plates of glass, by other accidental circum- 
stances, for instance, by slipping the plate on 
the side of the convex glass where.the pressure 
cannot be so strong as in the centre, all the 
gradations above described can be produced in 
succession. 

442. 

In order to observe the phenomenon it is 
necessary to look obliquely on the surface where 
it appears. But, above all, it is to be remarked 
that by stooping still more, and looking at the 
appearance under a more acute .angle, the 
circles not only grow larger but other circles are 
developed from the centre, of which no trace is 
to be discovered when we look perpendicularly, 
even through the strongest magnifiers. 



Digitized by 



Google 



184 EPOPTICAL COLOURS. 

443. 

In order to exhibit the phenomenon in its 
greatest beauty, the utmost attention should be 
paid to the cleanness of the glasses. If the ex- 
periment is made with plate-glass adapted for 
mirrors, the glass should be handled with gloves. 
The inner surfaces, which must come in contact 
with the utmost nicety, may be most conve- 
niently cleaned before the experiment, and the 
outer surfaces should be kept clean while the 
pressure is increased. 

444. 

From what has been said it will be seen that 
an exact contact of two smooth surfaces is 
necessary. ^Polished glasses are best adapted 
for the; purpose. Plates of glass exhibit the 
most brilliant colours when they fit closely 
together, and for this reason the phenomenon 
will increase in beauty if exhibited under an 
air-pump, by exhausting the air. 

445. 

The appearance of the coloured rings may be 
produced in the greatest perfection by placing a 
convex and concave glass together which have 
been ground on similar segments^f circles. I 
have never seen the efiect more brilliant than 
with the object-glass of an achromatic telescope, 



Digitized by 



Google 



EPOPTICAL COLOURS. 185 

Id which the crown-glass and flint-glass were 
necessarily in the closest contact. 

446. 

A remarkable appearance takes place when 
dissimilar surfaces are pressed together; for 
example, a polished crystal and a plate of 
glass. The appearance does not at all exhibit 
itself in large flowing waves, as in the combina- 
tion of glass with glass, but it is small and 
angular, and, as it were, disjointed: thus it 
appears that the surface of the polished crystal, 
which consists of infinitely small sections of 
lamellae, does not come so uninterruptedly in 
contact with the glass as another glass-plate 
would. 

447. 

The appearance of colour vanishes on the 
strongest pressure, which so intimately unites 
the two surfaces that they appear to make but 
one substance. It is this which occasions the 
dark centre, because the pressed lens no longer 
reflects any light from this point, for the very 
same point, when seen against the light, is per- 
fectly clear and transparent. On relaxing the 
pressure, the colours, in like manner, gradually 
diminish, and disappear entirely when the sur- 
faces are separated. 



Digitized by 



Google 



186 EPOPTICAL COLOURS. 

448. 
These same appearances occur in two similar 
cases. If entirely transparent masses become 
partially separated^ the surfaces of their parts 
being still sufficiently in contact, we see the 
same circles and waves more or less. They may 
be produced in great beauty by plunging a hot 
mass of glass in water ; the different fissures and 
cracks enabling us to observe the colours in 
various forms. Nature often exhibits the same 
phenomena in split rock crystals. 

449. 
This appearance, again, frequently displays 
itself in the mineral world in those kinds of 
stone which by nature have a tendency to ex- 
foliate. These original lamellae are, it is true, 
so intimately united, that stones of this kind 
appear altogether transparent and colourless, 
yet, the internal layers become separated, from 
various accidental causes, without altogether 
destroying the contact: thus the appearance, 
which is now familiar to us by the foregoing 
description, often occurs in nature, particularly 
in calcareous spars; the specularis, adularia, 
and other minerals of similar structure. Hence 
it shows an ignorance of the proximate causes 
of an appearance so often accidentally produced, 
to consider it so important in mineralogy, and 
to attach especial value to the specimens ex- 
hibiting it. 



Digitized by 



Google 



EPOPTICAL COLOURS. 187 

450. 

We have yet to speak of the very remarkable 
inversion of this appearance, as related by men 
of science. If> namely, instead of looking at 
the colours by a reflected light, we examine 
them by a transmitted light, the opposite colours 
are said to appear, and in a mode corresponding 
with that which we have before described as 
physiological ; the colours evoking each other. 
Instead of blue, we should thus see red-yellow ; 
instead of red, green, &c., and vice versa. We 
reserve experiments in detail^ the rather as we 
have ourselves still some doubts on this point. 

451. 

If we were now called upon to give some ge- 
neral explanation of these epoptical colours, as 
they appear under the first condition, and to 
show their connexion with the previously de- 
tailed physical phenomena, we might proceed to 
do so as follows : — 

452.' 

The glasses employed for the experiments are 
to be regarded as the utmost possible practical 
approach to transparence. By the intimate 
contact, however, occasioned by the pressure 
applied to them, their surfaces, we are per- 
suaded, immediately become in a very slight 
degree dimmed. Within this semi-transparence 



Digitized by 



Google 



188 EPOPTICAL COLOURS. 

the colours immediately appear, and every circle 
comprehends the whole scale ; for when the two 
opposites, yellow and blue, are united by their 
red extremities, pure red appears : the green, 
on the other hand, as in prismatic experiments, 
when yellow and blue touch. 

453. 

We have already repeatedly found that where 
colour exists at all, the whole scale is soon 
called into existence; a similar principle may be 
said to lurk in the nature of every physical 
phenomenon ; it already follows, from the idea 
of polar opposition, from which an elementary 
unity or completeness results. 

454. 

The fact that a colour exhibited by trans- 
mitted light is different from that displayed by 
reflected light, reminds us of those dioptrical 
colours of the first class which we found were 
produced precisely in the same way through 
semi-opacity. That here, too, a diminution of 
transparency exists there can scarcely be a 
doubt ; for the adhesion of the perfectly smooth 
plates of glass (an adhesion so strong that they 
remain hanging to each other) produces a de- 
gree of union which deprives each of the two 
surfaces, in some degree, of its smoothness and 
transparence. The fullest proof may, however. 



Digitized by 



Google 



EPOPTICAL C0L0UB8. 189 

be found in the fact that in the centre, where 
the lens is most istrongly pressed on the other 
glass, and where a perfect union is accom- 
plished, a complete transparence takes place, 
in which we no longer perceive any colour. All 
this may be hereafter confirmed in a recapitula-* 
tion of the whole. 



455. 



Digitized by 



Google 



190 EPOPTICAL COLOURS. 

towards the centre, the blue colour vanishes 
last. 

457. 

The phenomenon appears most readily between 
the minute lines, which the action of passing 
the fingers leaves on the clear surface ; a some- 
what rough state of the surface of the glass is 
otherwise requisite. On some glass the appear- 
ance may be produced by merely breathing ; in 
other cases the wiping with the fingers is neces- 
sary : I have even met with polished mirror- 
glasses, one side of which immediately showed 
the colours vividly; the other not. To judge 
from some remaining pieces, the former was ori- 
ginally the front of the glass, the latter the side 
which was covered with quicksilver. 

458. 

These experiments may be best made in cold 
weather, because the glass may be more quickly 
and distinctly breathed upon, and the breath 
evaporates more suddenly. In severe frost the 
phenomenon may be observed on a large scale 
while travelling in a carriage ; the glasses being 
well cleaned, and all closed. The breath of the 
persons within is very gently diffused over the 
glass, and immediately produces the most vivid 
play of colours. How far they may present a^ 
regular succession I have not been able to re- 



Digitized by 



Google 



EPOPTICAL COLOUBS. 191 

mark ; but they appear particularly vivid when 
they have a dark object as a background. This 
alternation of colours does not, however, last 
long; for as soon as the breath gathers in 
drops, or freezes to points of ice, the appear- 
ance is at once at an end. 

459. 

Third condition.— The two foregoing experi- 
ments of the pressure and breathing may be 
united ; namely, by breathing on a plate of glass, 
and immediately after pressing the other upon it. 
The colours then appear as in the case of two 
glasses unbreathed upon, with this difference, 
that the moisture occasions here and there an 
interruption of the undiilations. On pushing 
one glass away from the other the moisture ap- 
pears iridescent as it evaporates. 

460. 

It might, however, be asserted that this com- 
bined experiment exhibits no more than each 
single experiment; for it appears the colours 
excited by pressure disappear in proportion as 
the glasses are less in contact, and the moisture 
then evaporates with its owu colours. 

461. 

Fourth condition. — Iridescent appearances 
are observable in almost all bubbles ; soap- 



Digitized by 



Google 



192 EPOPTICAL C0L0UB8. 

bubbles are the most commonly known, and the 
effect in question is thus exhibited in the easiest 
mode ; but it may be observed in wine, beer, in 
pure spirit, and again, especially, in the froth of 
chocolate. 

462. 

As in the above cases we required an infi- 
nitely narrow space between two surfaces which 
are in contact, so we can consider the pellicle of 
the soap-bubble as an infinitely thin lamina be- 
tween two elastic bodies ; for the appearance in 
fact takes place between the air within, which 
distends the bubble, and the atmospheric air. 

463. 

The bubble when first produced is colourless ; 
then coloured stripes, like those in marble 
paper, begin to appear : these at length spread 
over the whole surface, or rather are driven 
round it as it is distended. 

464. 

In a single bubble, suffered to hang from the 
straw or tube, the appearance of colour is diffi- 
cult to observe, for the quick rotation prevents 
any accurate observation, and all the colours 
seem to mix together ; yet we can perceive that 
the colours begin at the orifice of the tube. The 
solution itself may, however, be blown into care^ 



Digitized by 



Google 



BPOPTICAL COLOURS* 193 

fiilly, so that only one bubble shall appear. This 
remains white (colourless) if not much agitated ; 
but if the solution is not too watery^ circles ap- 
pear round the perpendicular axis of the bubble; 
these being near each other^ are commonly com- 
posed alternately of green and red. Xastly, 
several bubbles may be produced together by 
the same means ; in this case the colours appear 
on the sides where two bubbles have pressed 
each other flat. 

465. 

The bubbles of chocolate-froth may perhaps 
be even more conveniently observed than those 
of soap; though smaller, they remain longer. 
In these, owing to the heat, an impulse, a move- 
ment, is produced and sustained, which appears 
necessary to the development and succession 
of the appearances. 

466. 

If the bubble is small, or shut in between, 
others, coloured lines chase each other over the 
surface, resembling marbled paper ; all the co- 
lours of the scale are seen to pass through each 
other ; the pure, the augmented, the combined, 
all distinctly clear and beautiful. In small 
bubbles the appearance lasts for a considerable 
time. 



Digitized by 



Google 



194 EPOPTIGAL COLOURS. • 

467, 

If the bubble is larger, or if it becomes by 
degrees detached, owing to the bursting of others 
near, we perceive that this impulsion and at- 
traction of the colours has, as it were, an end in 
view ; for on the highest point of the bubble we 
see a small circle appear, which is yellow in the 
centre ; the other remaining coloured lines move 
constantly round this with a vermicular action. 

468. 

In a short time the circle enlarges and sinks 
downwards on all sides; in the centre the 
yellow remains; below and on the outside it 
becomes red, and soon blue ; below this again ap- 
pears a new circle of the same series of colours : 
if they approximate sufficiently; a green is pro- 
duced by the union of the border-colours. 

469. 

When I could count three such leading cir- 
cles, the centre was colourless, and this space 
became by degrees larger as the circles sank 
lower, till at last the bubble burst. 

470. 

Fifth condition. — ^Very delicate pellicles may 
be formed in various ways : on these films we 
discover a very lively play of colours, either in 
the usual order, or more confusedly passing 
through each other. The water in which lime 



Digitized by 



Google 



EPOPTICAL COLOURS. 195 

has been slaked soon skims over with a coloured 
pellicle: the same happens on the surface of 
stagnant water, especially if impregnated with 
iron. The lamellae of the fine tartar which 
adheres to bottles, especially in red French 
wine, exhibit the most brilliant colours, on 
being exposed to the light, if carefully detached. 
Drops of oil on water, brandy, and other fluids, 
produce also similar circles and brilliant efiects : 
but the most beautiful experiment that can be 
made is the following : — Let aqua fortis, not too 
strong, be poured into a flat saucer, and then 
with a brush drop on it some of the varnish 
used by engravers to cover certain portions 
during the process of biting their plates. After 
quick commotion there presently appears a film 
which spreads itself out in circles, and imme- 
diately produces the most vivid appearances of 
colour. 

471. 

Sixth condition. — When metals are heated, 
colours rapidly succeeding each other appear on 
the surface : these colours can, however, be ar- 
rested at will. 

472. 

If a piece of polished steel is heated, it will, 
at a certain degree of warmth, be overspread 
with yellow. If taken suddenly away from the 
fire, this yellow remains. 

o2 



Digitized by 



Google 



196 EPOPTICAL COLOURS. 

473. 

As the steel becomfes hotter, the yellow ap- 
pears darker, intenser, and presently passes into 
red. This is difficult to arrest, for it hastens 
very quickly to bright blue. 

474. 

This beautiful blue is to be arrested if the 
steel is suddenly taken out of the heat and bu- 
ried in ashes. The blue steel works are pro- 
duced in this way. If, again, the steel is held 
longer over the fire, it soon becomes a light blue, 
and so it remains. 

475. 

These colours pass like a breath over the 
plate of steel; each seems to fly before the 
other, but, in reality, each successive hue is 
constantly developed from the preceding one. 

476. 

If we hold a penknife in the flame of a light, 
a coloured stripe will appear across the blade. 
The portion of the stripe which was nearest to 
the flame is light blue; this melts into blue- 
red ; the red is in the centre ; then follow yellow- 
red and yellow. 

477. 
This phenomenon is deducible from the pre- 



Digitized by 



Google 



BPOPTICAL COLOURS. 197 

ceding ones ; for the portion of the blade next 
the handle is less heated than the end which is 
in the flame, and thus all the colours which in 
other cases exhibited themselves in succession, 
must here appear at once, and may thus be 
permanently preserved. 

478. 

Robert Boyle gives this succession of colours 
as follows : — " A florido flavo ad flavum saturum 
et rubescentem (quem artifices sanguineum vo- 
cant) inde ad languidum, postea ad saturiorem 
cyaneum." This would be quite correct if the 
words " languidus" and "saturior*' were to change 
places. How far the observation is correct, that 
the different colours have a relation to the de- 
gree of temper which the metal afterwards 
acquires, we leave to others to decide. The 
colours are here only indications of the different 
degrees of heat. — Note R. 

479. 

When lead is calcined, the surface is first 
greyish. This greyish powder, with greater 
heat, becomes yellow, and then orange. Silver, 
too, exhibits colours when heated ; the fracture 
of silver in the process of refining belongs to 
the same class of examples. When metallic 
glasses melt, colours in like manner appear on 
the surface. 



Digitized by 



Google 



198 EPOPTICAL COLOURS. 

480. 

Seventh condition. — When the surface of glass 
becomes decomposed. The accidental opacity 
(blindwerden) of glass has been already no- 
ticed : the term (blindwerden) is employed to 
denote that the surface of the glass is so affected 
as to appear dim to us. 

481. 
White glass becomes ''blind" soonest; cast, 
and afterwards polished glass is also liable to 
be so affected ; the bluish less, the green least. 

482. 

Of the two sides of a plate of glass one is 
called the mirror side ; it is that which in the 
oven lies uppermost, on which one may observe 
roundish elevations: it is smoother than the 
other, which is undermost in the oven, and on 
which scratches may be sometimes observed. 
On this account the mirror side is placed facing 
the interior of rooms, because it is less affected 
by the moisture adhering to it from within, than 
the other would be, and the glass is thus less 
liable to become " blind." 

483. 

This half-opacity or dimness of the glass as- 
sumes by degrees an appearance of colour 
which may become very vivid, and in which 



Digitized by 



Google 



BPOPTIGAL COLOURS. 199 

perhaps a certain succession, or otherwise regu* 
lar order, might be discovered 

484. 

Having thus traced the physical colours from 
their simplest effects to the present instances, 
where these fleeting appearances are found to 
be fixed in bodies, we are, in fact, arrived at the 
point where the chemical colours begin ; nay, 
we have in some sort already passed those limits;, 
a circumstance which may excite a favourable 
prejudice for the consistency of our statement. 
By way of conclusion to this part of our inquiry, 
we subjoin a general observation, which may 
not be without its bearing on the common con- 
necting principle of the phenomena that have 
been adduced. 

485. 

The colouring of steel and the appearances 
analogous to it, might perhaps be easily deduced 
from the doctrine of the semi-opaque mediums. 
Polished steel reflects light powerfully : we may 
consider the colour produced by the heat as a 
slight degree of dimness : hence a bright yellow 
must immediately appear ; this, as the dimness 
increases, must still appear deeper, more con- 
densed, and redder, and at last pure and ruby- 
red. The colour has now reached the extreme 
point of depth, and if we suppose the same de- 



Digitized by 



Google 



200 EPOPTICAL COLOURS. 

gree of semi-opacity still to continue, the dim- 
ness would now spread itself over a dark ground, 
first producing a violet, then a dark-blue, and at 
last a light-blue, and thus complete the series of 
the appearances. 

We will not assert that this mode of explana- 
tion will suffice in all cases; our object is rather 
to point out the road by which the all-compre- 
hensive formula, the very key of the enigma, 
may be at last discovered.^— Note S. 



Digitized by 



Google 



201 
PART III. 

CHEMICAL COLOURS. 

486. 

We give this denomination to colours which we 
can produce, and more or less fix, in certain 
bodies; which we can render more intense, 
which we can again take away and communicate 
to other bodies, and to which, therefore, we 
ascribe a certain permanency : duration is their 
prevailing characteristic. 

487. 

In this view the chemical colours were for- 
merly distinguished with various epithets ; they 
were called colores proprii, corporei, materiales, 
veriy permanentes, fittu 

488. 

In the preceding chapter we observed how 
the fluctuating and transient nature of the phy- 
sical colours becomes gradually fixed, thus 
forming the natural transition to our present 
subject. 

489. 
Colour becomes fixed in bodies mbre or less 
permanently ; superficially, or thoroughly. 

490. 
All bodies are susceptible of colour ; it can 



Digitized by 



Google 



SOS CHEMICAL CONTRAST. 

either be excited, rendered intense, and gra* 
dually fixed in them, or at least communicated 
to them. 



XXXIV. 



CHEMICAL CONTBAST. 
491. 

In the examination of coloured appearances we 
had occasion everywhere to take notice of a 
principle of contrast : so again, in approaching 
the precincts of chemistry, we find a chemical 
contrast of a remarkable nature. We speak 
here, with reference to our present purpose, 
only of that which is comprehended under the 
general names of acid and alkali. 

492. 

We characterised the chromatic contrast, in 
conformity with all other physical contrasts as 
a more and less ; ascribing the plus to the yellow 
side, the minus to the blue; and we now find 
that these two divisions correspond with the 
chemical contrasts. The yellow and yellow-red 
afiect the acids, the blue and blue-red the 
alkalis; thus the phenomena of chemical co- 
lours, although still necessarily mixed up with 



Digitized by 



Google 



CHEMICAL CONTRABT. . 203 

Other considerations^ admit of being traced with 
sufficient simplicity. 

493. 

The principal phenomena in chemical colours 
are produced by the oxydation of metals, and it 
will be seen how important this consideration is 
at the outset. Other facts which come into the 
account, and which are worthy of attention, will 
be examined under separate heads ; in doing 
this we, however, expressly state that we only 
propose to offer some preparatory suggestions to 
the chemist in a very general way, without 
entering into the nicer chemical problems and 
questipns, or presuming to decide on them. Our 
object is only to give a sketch of the mode in 
which, according to our conviction, the chemical 
theory of colours may be connected with general 
physics. 



XXXV. 

WHITE. 

494. 
In treating of the dioptrical colours of the first 
class (155) we have already in some degree anti- 
cipated this subject. Transparent substances 



Digitized by 



Google 



204 CHEMICAL CONTRAST. 

may be said to. be in the highest class of inor- 
ganic matter. With these, colourless semi- 
transparence is closely connected, and white 
may be considered the last opaque degree of 
this. 

495. 

Pure water crystallised to snow appears 
white, for the transparence of the separate 
parts makes no transparent whole. Various 
crystallised salts, when deprived to a certain 
extent of moisture, appear as a white powder. 
The accidentally opaque state of a pure trans- 
parent substance might be called white; thus 
pounded glass appears as a white powder. The 
cessation of a combining power, and the ex- 
hibition of the atomic quality of the substance 
might at the same time be taken into the ac- 
count. 

496. 

The known undecomposed earths are, in their 
pure state, all white. They pass to a state 
of transparence by natural crystallization. Silex 
becomes rock-crystal ; argile, mica ; magnesia, 
talc ; calcareous earth and barytes appear trans- 
parent in various spars. — Note T. 

497. 
As in the colouring of mineral bodies the 



Digitized by 



Google 



CHEMICAL CONTRAST. 205 

metallic oxydes will often invite our attention, 
we observe, in conclusion, that metals, when 
slightly oxydated, at first appear white, as lead 
is converted to white lead by vegetable acid. 



XXXVI. 



BLACK. 

498. 

Black is not exhibited in so elementary a state 
as white. We meet with it in the vegetable 
kingdom in semi-combustion ; and charcoal, a 
substance especially worthy of attention on 
other accounts, exhibits a black colour. Again, 
if woods — for example, boards, owing to the 
action of light, air, and moisture, are deprived 
in part of their combustibility, there appears 
first the grey then the black colour. So again, 
we can convert even portions of animal sub- 
stance to charcoal by semi-combustion. 

499. 

In the same manner we often find that a sub- 
oxydation takes place in metals when the black 
colour is to be produced. Various metals, par- 
ticularly iron, become black by slight oxyda- 



Digitized by 



Google 



200 CHEMICAL CONTRAST. 

tion, by vinegar, by mild acid fermentations; 
for example, a decoction of rice, &c. 

500. 

Again, it may be inferred that a de-oxydation 
may produce black. This occurs in the prepa- 
ration of ink, which becomes yellow by the 
solution of iron in strong sulphuric acid, but 
when partly de-oxydised by the infusion of gall- 
nuts, appears black. 



XXXVII. 

FIRST EXCITATION OF COLOUR. 
501. 

In the division of physical colours, where semi- 
transparent mediums were considered, we saw 
colours antecedently to white and black. In 
the present case we assume a white and black 
already produced and fixed ; and the question 
is, how colour can be excited in them ? 

502. 

Here, too, we can say, white that becomes 
darkened or dimmed inclines to yellow ; black, 
as it becomes lighter, inclines to blue. — NotelJ. 



/Google 



FIRST SXCITJLTION OF COLOUR. 207 

503. 

Yellow appears on the active (plus) side, im- 
mediately in the light, the bright, the white. 
All white surfaces easily assume a yellow tinge ; 
paper, linen, wool, silk, wax : transparent fluids 
again, which have a tendency to combustion, 
easily become yellow; in other words they 
easily pass into a very slight state of semi-trans- 
parence. 

504. 

So again the excitement on the passive side, 
the tendency to obscure, dark, black, is imme- 
diately accompanied with blue, or rather with a 
reddish-blue. Iron dissolved in sulphuric acid, 
and much diluted with water, if held to the 
light in a glass, exhibits a beautiful violet colour 
as soon as a few drops only of the infusion of 
gall-nuts are added. This colour presents the 
peculiar hues of the dark topaz, the orphninon 
of a burnt-red, as the ancients expressed it. 

505. 
Whether any colour can be excited in the 
pure earths by the chemical operations of na- 
ture and art, without the admixture of metallic 
oxydes, is an important question, generally, in- 
deed, answered in the negative. It is perhaps 
connected with the question— to what extent 



Digitized by 



GoDgle 



208 FIRST EXCITATION OF COLOUR. 

changes may be produced in the earths through 
oxydation ? 

506. 

Undoubtedly the negation of the above ques- 
tion is confirmed by the circumstance that 
wherever mineral colours are found, some trace 
of metal^ especially of iron, shows itself; we are 
thus naturally led to consider how easily iron 
becomes oxydised, how easily the oxyde of iron 
assumes different colours, how infinitely divisi- 
ble it is, and how quickly it communicates its 
colour. It were to be wished, notwithstanding, 
that new experiments could be made in regard 
to the above point, so as either to confirm or 
remove any doubt. 

507. 

However this may be, the susceptibility of 
the earths with regard to colours already existing 
is very great ; aluminous earth is thus particu- 
larly distinguished. 

608. 

In proceeding to consider the metals, which 
in the inorganic world have the almost exclu- 
sive prerogative of appearing coloured, we 
find that, in their pure, independent, natural 
state, they are already distinguished from the 



Digitized by 



Google 



FIRST EXCITATION OF COLOURS. 209 

pure earths by a tendency to some one colour or 
other. 

609. 

While silver approximates most to pure white, 
— nay, really represents pure white, heightened 
by metallic splendor, — steel, tin, lead, and so 
forth, incline towards pale blue-grey ; gold, on 
the other hand, deepens to pure yellow, copper 
approaches a red hue, which, under certain 
circumstances, increases almost to bright red, 
but which again returns to a yellow golden 
colour when combined with zinc. 

510. 

But if metals in their pure state have so 
specific a determination towards this or that 
exhibition of colour, they are, through the effect 
of oxydation, in some degree reduced to a com- 
mon character ; for the elementary colours now 
come forth in their purity, and although this or 
that metal appears to have a particular tend- 
ency to this or that colour, we find some that 
can go through the whole circle of hues, others, 
that are capable of exhibiting more than one 
colour; tin, however, is distinguished by its 
comparative inaptitude to become coloured. 
We propose to give a table hereafter, showing 
how far the different metals can be more or less 
made to exhibit the different colours. 



Digitized by 



Google 



210 FIRST EXCITATION OF COLOURS. 

61L 

When the clean, smooth surface of a pnre 
metal, on being heated, becomes overspread with 
a mantling colour, which passes through a series 
of appearances as the heat increases, this, we are 
persuaded, indicates the aptitude of the metal 
to pass through the whole range of colours. We 
find this phenomenon most beautifully exhibited 
in polished steel ; but silver, copper, brass, lead, 
and tin, easily present similar appearances. A 
superficial oxydation is probably here taking 
place, as may be inferred from the effects of the 
operation when continued, especially in the 
more easily oxydizable metals. 

512. 

The same conclusion may be drawn from the 
fact that iron is more easily oxydizable by acid 
liquids when it is red hot, for in this case the 
two eflects concur with each other. We observe, 
again, that steel, accordingly as it is hardened 
in different stages of its colorification, may ex- 
hibit a difference of elasticity: this is quite 
natural, for the various appearances of colour 
indicate various degrees of heat.* 

513. 
If we look beyond this superficial mantling, 

♦ See par. 478. 



Digitized by 



Google 



FIB8T BXCITATIOK OF COLOURS. 211 

this pellicle of colour, we obaerve that as metald 
are oxydized throughout their masses, white or 
black appears with the first degree of heat, as 
may be seen in white lead, iron, and quicksilver. 

614. 

If we examine furtheri and look for the actual 
exhibition of colour, we find it most frequently 
on the plus side. The mantling, so often men- 
tioned, of smooth metallic surfaces begins with 
yellow. Iron passes presently into yellow ochre, 
lead from white lead to massicot, quicksilver 
from sethiops to yellow turbith. The solutions 
of gold and platinum in acids are yellow. 

515. 

The exhibitions on the minw side are less fre* 
quent Copper slightly oxydized appears blue. 
la the preparation of Prussian-blue^ alkalis ve 
eiaployed. 

516. 

Generally* however, these appearances of co- 
lour are of so mutable a nature that chemists 
look upon them as deceptive tests, at least in 
the nicer gradations. Fo|r ourselves, as we can 
only treat of these matters in a general way, we 
merely observe that the appearances of colour 
in metals may be classed according to their 

p2 



Digitized by 



Google 



212 AUGMENTATION OF COLOUR. 

origiD, manifold appearance, and cessation, as 
various results of oxydation, hyper*oxydation, 
ab-oxydation, and de-oxydation.'*' 



XXXVIII. 

AUGMENTATION OF COLOUE.t 

617. 
The augmentation of colour exhibits itself as a 
condensation, a fulness, a darkening of the hue. 
We have before seen, in treating of colourless 
mediums, that by increasing the degree of opa- 
city in the medium, we can deepen a bright 
object from the lightest yellow to the intensest 
ruby-red. Blue, on the other hand, increases 
to the most beautiful violet, if we rarefy and 
diminish a semi-opaque medium, itself lighted, 
but through which we see darkness (150, 151). 

618. 

If the colour is positive, a similar colour ap- 
pears in the intenser state. Thus if we fill a 
white porcelain cup with a pure yellow liquor, 
the fluid will appear to become gradually redder 

* Ab these tenns are afterwards referred to (par. 525), it was 
necessary to preserve- them. 

t Steigerung, literally gradual ascent. See the note to par. 523. 



Digitized by 



Google 



AUGMBNTATION OF COLOUR. 213 

towards the bottom, and at last appears orange. 
If we pour a pure blue solution into another 
cup, the upper portion will exhibit a sky-blue, 
that towards the bottom, a beautiful violet. If 
the cup is placed in the sun, the shadowed side, 
even of the upper portion, is already violet. If 
we throw a shadow with the hand, or any 
other substance, over the illumined portion, the 
shadow in like manner appears reddish. 

519. 

This is one of the most important appearances 
connected with the doctrine of colours, for we 
here manifestly find that a difference of quan- 
tity produces a corresponding qualified impres- 
sion on our senses. In speaking of the last 
class of epoptical colours (452, 485), we stated 
our conjecture that the colouring of steel might 
perhaps be traced to the doctrine of the semi- 
transparent mediums, and we would here again 
recall this to the reader's recollection. 

520. 

All chemical augmentation of colour, again, 
is the immediate consequence of continued ex- 
citation. The augmentation advances constantly 
and unremittingly, and it is to be observed that 
the increase of intenseness is most common on 
the plus side. Yellow iron ochre increases, as 
well by fire as by other operations, to a very 



Digitized by 



Google 



214 AUQMBNTATION OF COLOUB. 

Strong red: massicot is increased to red lead» 
turbith to vermilion, which last attains a Tery 
high degree of the yellow* red. An intimate 
saturation of the metal by the acid, and its se* 
paration to infinity, take place together with the 
above effects. 

521. 

The augmentation on the minus side is less 
frequent; but we observe that the more pure 
and condensed the Prussian-blue or cobalt glass 
is prepared, the more readily it assumes a red- 
dish hue and inclines to the violet. 

622. 

The French have a happy expression for the 
less perceptible tendency of yellow and blue 
towards red : they say the colour has *' un oeil 
de rouge," which we might perhaps express by 
a reddish glance (einen rothlichen blick). 



XXXIX. 

CULMINATION* 

523. 

This is the consequence of still progressing aug- 
mentation. Red, in which neither yellow nor 

* CtUmznaiion^ the original word. It might have boen ren- 



Digitized by 



Google 



CULMINATION. 215 

blue is to be detected, here constitutes the 
ax^me. 

524. 

If we wish to select a striking example of a 
culmination on the plus side, we again find it 
in the coloured steel, which attains the bright 
red acme, and can be arrested at this point. 

525. 

Were we here to employ the terminology be- 
fore proposed, we should say that the first oxy- 
dation produces yellow, the hyper-oxydation 
yellow-red ; that here a kind of maximum exists, 
and that then an ab-oxydation, and lastly a de- 
oxydation takes place. 

526. 

High degrees of oxydation produce a bright 
red. Gold in solution, precipitated by a solution 
of tin, appears bright red : oxyde of arsenic, in 
combination with sulphur, produces a ruby 
colour. 

527. 

How far, however, a kind of sub-oxydation 
may co-operate in some culminations, is matter 
for inquiry ; for an influence of alkalis on the 

dered maximum of colour^ but as the author Bupposes an ascent 
through yellow and blue to red, hb meaning is better expressed 
by his own term. 



Digitized by 



Google 



216 CULMINATION. 

yellow-red also appears to produce the culmina- 
tion ; the colour reaching the acme by being 
forced towards the minus side. 

528. 
The Dutch prepare a -colour known by the 
name of vermilion, from the best Hungarian 
cinnabar, which exhibits the brightest yellow- 
red. This vermilion is still only a cinnabar, 
which, however, approximates the pure red, and 
it may be conjectured that alkalis are used to 
bring it nearer to the culminating point 

529. 
Vegetable juices, treated in this way, offer 
very striking examples of the above effects. 
The colouring-matter of turmeric, annotto, dyer's 
saffron,* and other vegetables, being extracted 
with spirits of wine, exhibits tints of yellow, 
yellow-red, and hyacinth-red; these, by the ad- 
mixture of alkalis, pass to the culminating point, 
and even beyond it to blue-red. 

530. 
No instance of a culmination on the mintM 
side has come to my knowledge in the mineral 
and vegetable kingdoms. In the animal king- 
dom the juice of the murex is remarkable; of 
its augmentation and culmination on the minus 
side, we shall hereafter have occasion to speak. 

* Curcuma, Bixa Orellana, Carthamus Tinctorius. 



Digitized by 



Google 



217 



XL. 

FLUCTUATION. 

531. 
The mutability of colour is so great, that even 
those pigments, which may have been considered 
to be defined and arrested, still admit of slight 
variations on one side or the other. This muta- 
bility is most remarkable near the culminating 
point, and is effected in a very striking manner 
by the alternate employment of acids and alkalis. 

632. 

To express this appearance in dyeing, the 
French make use of the word •• virer,'* to turn 
from one side to the other; they thus very 
adroitly convey an idea which others attempt to 
express by terms indicating the component 
hues. 

533. 

The effect produced with litmus is one of the 
most known and striking of this kind. This 
colouring substance is fendered red-blue by 
means of alkalis. The red-blue is very readily 
changed to red-yellow by means of acids, and 
again returns to its first state by again employ- 
ing alkalis. The question whether a culmi- 
nating point is to be discovered and arrested by 



Digitized by 



Google 



218 FLUCTUATION. 

nice experiments, is left to those who are prac- 
tised in these operations. Dyeing, especially 
scarlet-dyeing, might afford a variety of ex- 
amples of this fluctuation. 



XLl. 

PASSAGE THROUGH THE WHOLE SCALE. 
534. 

The first excitation and gradual increase of 
colour take place more on the plus than on the 
mimts side. So, also, in passing through the 
whole scale, colour exhibits itself most on the 
plw side. 

535. 

A passage of this kind, regular and evident to 
the senses, from yellow through red to blue, is 
apparent in the colouring of steel. 

636. 

The metals may be arrested at various points 
of the colorific circle by various degrees and 
kinds of oxydation. 

537. 
As they also appear green, a question arises 
whether chemists know any instance in the 



Digitized by 



Google 



PASSAGE THBOUGH THE WHOLE SCALE. 219 

mineral kingdom of a constant transition from 
yellow, through grieen, to blue, and vice versd. 
Oxyde of iron, melted with glass, produces first 
a green, and with a more powerful heat, a blue 
colour. 

638. 

We may here observe of green generally, that 
it appears, especially in an atomic sense, and 
certainly in a pure state, when we mix blue and 
yellow : but, again, an impure and dirty yellow 
soon gives us the impression of green ; yellow 
and black already produce green ; this, however, 
is owing to the affinity between black and blue. 
An imperfect yellow, such as that of sulphur, 
gives us the impression of a greenish hue : thus, 
again, an imperfect blue appears green. The 
green of wine bottles arises, it appears, from an 
imperfect union of the oxyde of iron with the 
glass. If we produce a more complete union 
by greater heat, a beautiful blue-glass is the 
result. 

539. 

From all this it appears that a certain chasm 
exists in nature between yellow and blue, the 
opposite characters of which, it is true, may be 
done away atomically by due immixture, and, 
thus combined, to green; but the true recon- 
ciliation between yellow and blue, it seems, 
only takes place by means of red. 



Digitized by 



Google 



220 PASSAGE THROUGH THE WHOLE SCALE. 

540. 

The process, however, which appears un- 
attainable in inorganic substances, we shall find 
to be possible when we turn our attention to 
organic productions ; for in these, the passage 
through the whole circle from yellow, through 
green and blue, to red, really takes place. 



XLII. 

INVERSION. 



541. 

Again, an immediate inversion or change to 
the totally opposite hue, is a very remarkable 
appearance which sometimes occurs ; at present, 
we are merely enabled to adduce what follows. 

642. 

The mineral chameleon, a name which has 
been given to an oxyde of manganese, may be 
considered, in its perfectly dry state, as a green 
powder. If we strew it in water, the green 
colour displays itself very beautifully in the first 
moment of solution, but it changes presently to 
the bright red opposite to green, without any 
apparent intermediate state. 



Digitized by 



Google 



INYEBSION. 221 

543. 

The same occurs with the sympathetic ink, 
which may be considered a reddish liquid, but 
which, when dried by warmth, appears as a 
green colour on paper. 

644. 

In fact, this phenomenon appears to be owing 
to the conflict between a dry and moist state, as 
has been already observed, if we are not mis- 
taken, by the chemists. We may look to the 
improvements of time to point out what may 
further be deduced from these phenomena, and 
to show what other facts they may be connected 
with. 



XLIII. 

FIXATION. 

645. 

Mutable as we have hitherto found colour to 
be, even as a substance, yet under certain cir- 
cumstances it may at last be fixed. 

546. 

There are bodies capable of being entirely 
converted into colouring matter : here it may be 
said that the colour fixes itself in its own sub- 



Digitized by 



Google 



222 FIXATION. 

Stance, stops at a certain point, and is there de- 
fined. Such colouring substances are found 
throughout nature ; the vegetable world affords 
a great quantity of examples, among which 
some are particularly distinguished* and may be 
considered as the representatives of the rest; 
such as, on the active side, madder, on the 
passive side, indigo. 

547. 

In order to make these materials available in 
use, it is necessary that the colouring quality in 
them should be intimately condensed, and the 
tinging substance refined, practically speaking, 
to an infinite divisibility. This is accomplished 
in various ways, and particularly by the well- 
known means of fermentation and decomposition. 

548. 

These colouring substances now attach them- 
selves again to other bodies. Thus, in the 
mineral kingdom they adhere to earths and 
metallic oxydes; they unite in melting with 
glasses ; and in this case, as the light is trans- 
mitted through them, they appear in the greatest 
beauty, while an eternal duration may be as- 
cribed to them. 

549. 

Tbey fSasten on vegetable and animal bodies 
with more or less power, and remain more or less 



Digitized by 



Google 



FIXATION. 223 

permanently ; partly owing to their nature, — as 
yellow, for instance, is more evanescent than 
blue,— or owing to the nature of the substance on 
which they appear. They last less in vegetable 
than in animal substances, and even within this 
latter kingdom there are again varieties. Hemp 
or cotton threads, silk or wool, exhibit very 
different relations to colouring substances. 

550. 

Here comes into the account the important 
operation of employing mordants, which may 
be considered as the intermediate agents be- 
tween the colour and the recipient substance ; 
various works on dyeing speak of this circum- 
stantially. Suffice it to have alluded to pro- 
cesses by means of which the colour retains a 
permanency only to be destroyed with the sub- 
stance, and which may even increase in bright- 
ness and beauty by use. 



XLIV. 

INTERMIXTURE, REAL. 
551. 

£vERY intermixture pre-supposes a specific 
state of colour ; and thus when we speak of in- 
termixture, we here understand it in an atomic 



Digitized by 



Google 



224 INTERMIXTURE, REAL. 

sense. We must first have before us certain 
bodies arrested at any given point of the colorific 
circle, before we can produce gradations by their 
union. 

552. 

Yellow, blue, and red, may be assumed as 
pure elementary colours, already existing ; from 
these, violet, orange, and green, are the simplest 
combined results. 

553. 

Some persons have taken much pains to de- 
fine these intermixtures more accurately, by 
relations of number, measure, and weight, but 
nothing very profitable has been thus accom- 
plished. 

554. 
Painting consists, strictly speaking, in the 
intermixture of such specific colouring bodies 
and their infinite possible combinations — com- 
binations which can only be appreciated by the 
nicest, most practised eye, and only accom- 
plished under its influence. 

555. 

The intimate combination of these ingredients 
is effected, in the first instance, through the most 
perfect comminution of the material by means 
of grinding, washing, &c., as well as by vehicles 



Digitized by 



Google 



INTERMIXTURE, REAL. 225 

or liquid mediums which hold together the pul- 
verized substance, and combine organically, 
as it were, the unorganic ; such are the oils, 
resins, &c. — Note V. 

556. 

If all the colours are mixed together they re- 
tain their general character as (rxisp^v, and as 
they are no longer seen next each other, no 
completeness, no harmon}^ is experienced ; the 
result is grey, which, like apparent colour, 
always appears somewhat darker than white, 
and somewhat lighter than black. 

557. 

This grey may be produced in various ways. 
By mixing yellow and blue to an emerald 
green, and then adding pure red, till all three 
neutralize each other ; or, by placing the primi- 
tive and intermediate colours next each other 
in a certain proportion, and afterwards mixing 
them. 

558. 

That all the colours mixed together produce 
white, is an absurdity which people have credu- 
lously been accustomed to repeat for a century, 
in opposition to the evidence of their senses. 

559. 
Colours when mixed together retain their 



Digitized by 



Google 



226 INTERMIXTURE, REAL. 

original darkness. The darker the colours, the 
darker will be the grey resulting from their 
union, till at last this grey approaches black. 
The lighter the colours the lighter will be the 
grey, which at last approaches white. 



XLV. 

INTERMIXTURE, APPARENT. 
560. 

The intermixture, which is only apparent, 
naturally invites our attention in connexion with 
the foregoing ; it is in many respects important, 
and^ indeed, the intermixture which we have 
distinguished as real, might be considered as 
merely apparent For the elements of which 
the combined colour consists are only too small 
to be considered as distinct parts. Yellow and 
blue powders mingled together appear green to 
the naked eye, but through a magnifying glass 
we can still perceive yellow and blue distinct 
from each other. Thus yellow and blue stripes 
seen at a distance, present a green mass; the 
same observation is applicable with regard to 
the intermixture of other specific colours. 

561. 
In the description of our apparatus we shall 



Digitized by 



Google 



INTERMIXTURE, APPARENT. 227 

have occasion to mention the wheel by means of 
which the apparent intennixture is produced 
by rapid movement. Various colours are ar- 
ranged near each other round the edge of a 
disk, which is made to revolve with velocity, 
and thus by having several such disks ready, 
every possible intermixture can be presented to 
the eye, as well as the mixture of all colours to 
grey, darker or lighter, according to the depth 
of the tints as above explained. 

562. 

Physiological colours admit, in like manner, 
of being mixed with others. If, for example, 
we produce the blue shadow (65) on a light 
yellow paper, the surface will appear green. 
The same happens with regard to the other 
colours if the necessary preparations are at* 
tended to. 

563. 
If, when the eye is impressed with visionary 
images that last for a while, we look on coloured 
surfaces, an intermixture also takes place ; the 
spectrum is determined to a new colour which 
is composed of the two. 

564. 

Physical colours also admit of combination. 
Here might be adduced the experiments in 

Q 2 



Digitized by 



Google 



228 INTERMIXTURE, APPARENT. 

which many-coloured images are seen through 
the prism, as we have before shown in detail 
(258, 284). 

565. 

Those who have prosecuted these inquiries 
have, however, paid most attention to the ap- 
pearances which take place when the prismatic 
colours are thrown on coloured surfaces. 

666. 

What is seen under these circumstances is 
quite simple. In the first place it must be re- 
membered that the prismatic colours are much 
more vivid than the colours of the surface on 
which they are thrown. Secondly, we have 
to consider that the prismatic colours may be 
either homogeneous or heterogeneous, with the 
recipient surface. In the former case the sur- 
face deepens and enhances them, and is itself 
enhanced in return, as a coloured stone is 
displayed by a similarly coloured foil. In the 
opposite case each vitiates, disturbs, and des- 
troys the other. 

567. 
These experiments may be repeated with 
coloured glasses, by causing the sun-light to 
shine through them on coloured surfaces. In 
every instance similar results will appear. 



Digitized by 



Google 



INTERMIXTURE, APPARENT. 229 
568. 

The same effect takes place when we look on 
coloured objects through coloured glasses ; the 
colours being thus according to the same con- 
ditions enhanced, subdued, or neutralized. 

569. 

If the prismatic colours are suffered to pass 
through coloured glasses, the appearances that 



Digitized by 



Google 



230 



XLVl. 

COMMUNICATION, ACTUAL. 

572. 

Having now provided the colouring materials, 
as before shown, a further question arises how 
to communicate these to colourless substances : 
the answer is of the greatest importance from 
the connexion of the object with the ordinary 
wants of men^ with useful purposes, and with 
commercial and technical interests. 

573. 

Here, again, the dark quality of every colour 
again comes into the account. From .a yellow 
that is very near to white, through orange, and 
the hue of minium to pure red and carmi^e, 
through all gradations of violet tf> the deepest 
blue which is almost identified with black, 
colour still increases in darkness. Blue once 
defined, admits of being diluted, made light, 
united with yellow, and then, as green, it ap- 
proaches the light side of the scale : but this is 
by no means according to its own nature. 

574. 

In the physiological colours we have already 
seen that they are less than the light, inasmuch 



Digitized by 



Google 



COMMUNICATION, ACTUAL. 231 

as they are a repetition of an impression of 
light, nay, at last they leave this impression 
quite as a dark. In physical experiments the 
employment of semi-transparent mediums, the 
effect of semi-transparent accessory images, 
taught us that in such cases we have to do with 
a subdued light, with a transition to darkness. 

575. 

In treating of the chemical origin of pigments 
we found that the same effect was produced on 
the very first excitement. The yellow tinge 
which mantles over the steel, already darkens 
the shining surface. In changing white lead to 
massicot it is evident that the yellow is darker 
than white. 

576. 

This process is in the highest degree delicate ; 
the growing intenseness, as it still increases, 
tinges the substance more and more intimately 
and powerfully, and thus indicates the extreme 
fineness, and the infinite divisibility of the 
coloured atoms. 

577. 

The colours which approach the dark side, 
and consequently, blue in particular, can be 
made to approximate to black ; in fact, a very 
perfect Prussian blue, or an indigo acted on by 
vitriolic acid appears almost as a black. 



Digitized by 



Google 



232 COMMUNICATION, ACTUAL. 

678. 

A remarkable appearance may be here ad- 
verted to ; pigments, in their deepest and most 
condensed state, especially those produced from 
the vegetable kingdom, such as the indigo just 
mentioned, or madder carried to its intensest 
hue, no longer show their own colour ; on the 
contrary, a decided metallic shine is seen on 
their surface, in which the physiological com- 
pensatory colour appears. 

579. 
All good indigo exhibits a copper-colour in its 
fracture, a circumstance attended to, as a known 
characteristic, in trade. Again, the indigo which 
has been acted on by sulphuric acid, if thickly 
laid on, or suffered to dry so that neither white 
paper nor the porcelain can appear through, 
exhibits a colour approaching to orange. 

680. 
The bright red Spanish rouge, probably pre- 
pared from madder, exhibits on its surface a 
perfectly green, metallic shine. If this colour, 
or the blue before mentioned, is washed with a 
pencil on porcelain or paper, it is seen in its 
real state owing to the bright ground shining 
through. 

681. • 
Coloured liquids appear black when no light 



Digitized by 



Google 



COMMUNICATION, ACTUAL. 233 

is transmitted through them, as we may easily 
see in cubic tin vessels with glass bottoms. In 
these every transparent-coloured infusion will 
appear black and colourless if we place a black 
surface under them. 

582. 

If we contrive that the image of a flame be 
reflected from the bottom, the image will appear 
coloured. If we lift up the vessel and sufier the 
transmitted light to fall on white paper under it, 
the colour of the liquid appears on the paper. 
Every light ground seen through such a coloured 
medium exhibits the colour of the medium. 

583. 

Thus every colour, in order to be seen, must 
have a light within or behind it Hence the 
lighter and brighter the grounds are, the more 
brilliant the colours appear. If we pass lac- 
varnish over a shining white metal surface, as 
the so-called foils are prepared, the splendor of 
the colour is displayed by this internally re- 
flected light as powerftilly as in any prismatic 
experiment ; nay, the force of the physical co- 
lours is owing principally to the circumstance 
that light is always acting with and behind 
them. 

• 584. 
Lichtenberg, who of necessity followed the 



Digitized by 



Google 



234 COMMUNICATION, ACTUAL. 

received theory, owing to the time and circum- 
stances in which he lived, was yet too good an 
observer, and too acute not to explain and clas- 
sify, after his fashion, what was evident to his 
senses. He says, in the preface to Delaval, " It 
appears to me also, on other grounds, probable, 
that our organ, in order to be impressed by a 
colour, must at the same time be impressed by 
all light (white)/' 

585. 

To procure white as a ground is the chief 
business of the dyer. Every colour may be 
easily communicated to colourless earths, espe- 
cially to alum : but the dyer has especially to 
do with animal and vegetable products as the 
ground of his operations. 

586. 

Everything living tends to colour — to local, 
specific colour, to effect, to opacity — pervading 
the minutest atoms. Everything in which life 
is extinct approximates to white (494), to the 
abstract, the general state, to clearness,**^ to 
transparence. 

587. 

How this is put in practice in technical opera- 
tions remains to be adverted to in the chapter 
on the privation of colour. With regard to the 

♦ VerklfijruDg, literally clarificaiion. 



Digitized by 



Google 



COMMUNICATION, APPARENT. 236 

communication of colour, we have especially to 
bear in mind that animals and vegetables^ in a 
living state, produce colours, and hence their 
substances, if deprived of colours, can the more 
readily re-assume them. 



XLVII. 

COMMUNICATION, APPARENT. 

588. 

The communication of colours, real as well as 
apparent, corresponds, as may easily be seen, 
with their intermixture : we need not, therefore, 
repeat what has been already sufficiently en- 
tered into. 

589. 

Yet we may here point out more circumstan- 
tially the importance of an apparent communi- 
cation which takes place by means of reflection. 
This phenomenon is well known, but still it is 
pregnant with inferences, and is of the greatest 
importance both to the investigator of nature 
and to the painter. 

590. 

Let a surface coloured with any one of the 
positive colours be placed in the sun, and let its 



Digitized by 



Google 



236 COMMUNICATION, APPARENT. 

reflection be thrown on other colourless objects. 
Tills reflection is a kind of subdued light, a 
half-light, a half-shadow, which, in a subdued 
state, reflects the colours in question. 

591. 

If this reflection acts on light surfaces, it is 
so far overpowered that we can scarcely per- 
ceive the colour which accompanies it ; but if it 
acts on shadowed portions, a sort of magical 
union takes place with the trxispS. Shadow is 
the proper element of colour, and in this case 
a subdued colour approaches it, lighting up, 
tinging, and enlivening it. And thus arises an 
appearance^ as powerful as agreeable, which 
may render the most pleasing service to the 
painter who knows how to make use of it 
These are the types of the so-called reflexes, 
which were only noticed late in the history of 
art, and which have been too seldom employed 
in their full variety. 

592. 

The schoolmen called these colours cohres na- 
tianales and intentionales, and the history of the 
doctrine of colours will generally show that the 
old inquirers already observed the phenomena 
well enough, and knew how to distinguish them 
properly, although the whole method of treating 
such subjects is very difierent from ours. 



Digitized by 



Google 



237 
XLVIII. 

EXTRACTION. 
593. 

Colour may be extracted from substances, 
whether they possess it naturally or by com- 
munication, in various ways. We have thus the 
power to remove it intentionally for a usefnl 
purpose, but, on the other hand, it often flies 
contrary to our wish. 

594. 

Not only are the elementary earths in their 
natural state white, but vegetable and animal 
substances can be reduced to a white state with- 
out disturbing their texture. A pure white is 
very desirable for various uses, as in the instance 
of our preferring to yse linen and cotton stufis 
uncoloured. In like manner some silk stufis, 
paper, and other substances, are the more agree- 
able the whiter they can be. Again, the chief 
basis of all dyeing consists in white grounds. 
For these reasons manufacturers, aided by acci- 
dent and contrivance, have devoted themselves 
assiduously to discover means of extracting 
colour: infinite experiments have been made 
in connexion with this object, and many im- 
portant facts have been arrived at. 



Digitized by 



Google 



238 EXTRACTION. 

595. 

It is in accomplishing this entire extraction of 
colour that the operation of bleaching consists, 
which is very generally practised empirically or 
methodically. We will here shortly state the 
leading principles. 

596. 

Light is considered as one of the first means 
of extracting colour from substances, and not 
only the sun-light, but the mere powerless day- 
light : for as both lights — the direct light of the 
sun, as well as the derived light of the sky — 
kindle Bologna phosphorus, so both act on co- 
loured surfaces. Whether the light attacks the 
colour allied to it^ and, as it were, kindles and 
consumes it, thus reducing the definite quality 
to a general state, or whether some other opera- 
tion, unknown to us, takes place, it is clear that 
light exercises a great power on coloured sur- 
faces, and bleaches them more or less. Here, 
however, the difierent colours exhibit a difierent 
degree of durability ; yellow, especially if pre- 
pared from certain materials, is, in this case, 
the first to fly. 

597, 
Not only light, but air, and especially water, 
act strongly in destroying colour. It has been 
even asserted that thread, well soaked and 



Digitized by 



Google 



EXTRACTION. 239 

spread oil the grass at night, bleaches better 
than that which is exposed, after soaking, to the 
sun-light. Thus, in this case, water proves to 
be a solving and conducting agent, removing the 
accidental quality, and restoring the substance 
to a general or colourless state. 

598. 

The extraction of colour is also effected by 
re-agents. Spirits of wine has a peculiar tend- 
ency to attract the juice which tinges plants, 
and becomes coloured with it often in a very 
permanent manner. Sulphuric acid is very effi- 
cient in removing colour, especially from wool 
^nd silk, and every one is acquainted with the 
use of sulphur vapours in bleaching. 

599. 

The strongest acids have been recommended 
more recently as more expeditious agents in 
bleaching. 

600. 

The alkaline re-agents produce the same 
effects by contrary means — lixiviums alone, oils 
and fat combined with lixiviums to soap, and 
so forth. 

601. 
Before we dismiss this subject, we observe 



Digitized by 



Google 



240 EXTRACTION. 

that it may be well worth while to make certain 
delicate experiments as to how far light and air 
exhibit their action in the removal of colour. It 
might be possible to expose coloured substances 
to the light under glass bells, without air^ or 
filled with common or particular kinds of air. 
The colours might be those of known fugacity, 
and it might be observed whether any of the 
volatilized colour attached itself to the glass or 
was otherwise perceptible as a deposit or preci- 
pitate ; whether, again, in such a case, this ap- 
pearance would be perfectly like that which had 
gradually ceased to be visible, or whether it had 
sufiered any change. Skilful experimentalists 
might devise various contrivances with a view 
to such researches. 

602. 

Having thus first considered the operations of 
nature as subservient to our purposes, we add a 
few observations on the modes in which they 
act against us. 

603. 

The art of painting is so circumstanced that 
the most beautiful results of mind and labour are 
altered and destroyed in various ways by time. 
Hence great pains have been always taken to 
find durable pigments, and so to unite them 
with each other and with their ground, that their 



Digitized by 



Google 



EXTRACTION. 241 

permanency might be further insured. The 
technical history of the schools of painting 
affords sufficient informiation on this point. 

604. 

We may here, too, mention a minor art, to 
which, in relation to dyeing, we are much in- 
debted, namely, the weaving of tapestry. As 
the manufacturers were enabled to imitate the 
most delicate shades of pictures, and hence 
often brought the most variously coloured ma- 
terials together, it was soon observed that the 
colours were not all equally durable, but that 
some faded from the tapestry more quickly than 
others. Hence the most diligent efforts were 
made to ensure an equal permanency to all the 
colours and their gradations. This object was 
especially promoted in France, under Colbert, 
whose regulations to this effect constitute an 
epoch in the history of dyeing. The gay dye 
which only aimed at a transient beauty, was 
practised by a particular guild. On the other 
hand, great pains were taken to define the 
technical processes which promised durability. 

And thus, after considering the artificial ex- 
traction, the evanescence, and the perishable 
nature of brilliant appearances of colour, we 
are again returned to the desideratum of per- 
manency. 



Digitized by 



Google 



242 



XLIX. 

NOMENCLATURE. 
605. 

After what has been adduced respecting the 
origin, the increase, and the affinity of colours, 
we may be better enabled to judge what nomen- 
clature would be desirable in future, and what 
might be retained of that hitherto in use. 

606. 

The nomenclature of colours, like all other 
modes of designation, but especially those em- 
ployed to distinguish the objects of sense, pro- 
ceeded in the first instance from particular to 
general, and from general back again to. par- 
ticular terms. The name of the species became 
a generic name to which the individual was 
again referred. 

607. 

This method might have been followed in 
consequence of the mutability and uncertainty 
of ancient modes of expression, especially since, 
in the early ages, more reliance may be sup- 
posed to have been placed on the vivid impres- 
sions of sense. The qualities of objects were 
described indistinctly, because they were im- 
pressed clearly on every imagination. 



Digitized by 



Google 



NOMENCLATURE. 243 

608. 

The pure chromatic circle was limited, it is 
true ; but, specific as it was, it appears to have 
been applied to innumerable objects, while it 
was circumscribed by qualifying characteristics. 
If we take a glance at the copiousness of the 
Greek and Roman terms, we shall perceive how 
mutaj^le the words were, and how easily each 
was adapted to almost every point in the colo- 
rific circle. — Note W. 



Digitized by 



Google 



244 NOMENCLATURE. 

611. 

If we were to add two other qualifying terms 
to each of these four, as thus — red-yellow, and 
yellow-red, red-blue and blue-red, yellow-green 
and green-yellow, blue-green and green-blue,* 
we should express the gradations of the chro- 
matic circle with sufficient distinctness ; and if 
we were to add the designations of light and 
dark, and again define, in some measure, the 
degree of purity or its opposite by the mono- 
syllables black, white, grey, brown, we should 
have a tolerably sufficient range of expressions 
to describe the ordinary appearances presented 
to us, without troubling ourselves whether they 
were produced dynamically or atomically. 

612. 

The specific and proper terms in use might, 
however, still be conveniently employed, and we 
have thus made use of the words orange and 
violet. We have in like manner employed the 
word ''purpur'* to designate a pure central red, 
because the secretion of the murex or ** purpura** 
is to be carried to the highest point of culmina- 
tion by the action of the sun-light on fine linen 
saturated with the juice. 

* This description is suffered to remain because it accounts for 
the terminology employed throughout. — ^T. 



Digitized by 



Google 



245 



L. 

MINERALS. 

613. 

The colours of minerals are all of a chemical 
nature, and thus the modes in which they are 
produced may be explained in a general way by 
what has been said on the subject of chemical 
colours. 



Digitized by 



Google 



246 MINERALS. 

at that these gradations should also be adopted 
as criterions, and that the artist should be in- 
vited to produce tinted patterns with which the 
objects of nature might be compared, and 
according to which they were to receive their 
designations. 

616. 

But, after all, the terminology of colours which 
has been introduced in mineralogy, is open to 
many objections. The terms, for instance, have 
not been borrowed from the mineral kingdom, 
as was possible enough in most cases, but 
from all kinds of visible objects. Too many 
specific terms have been adopted ; and in seek- 
ing to establish new definitions by combining 
these, the nomenclators have not reflected that 
they thus altogether efiace the image from the 
imagination, and the idea from the understand- 
ing. Lastly, these individual designations of 
colours, employed to a certain extent as ele- 
mentary definitions, are not arranged in the best 
manner as regards their respective derivation 
from each other : hence, the scholar must learn 
every single designation, and impress an almost 
lifeless but positive language on his memory. 
The further consideration of this would be too 
foreign to our present subject* 

* These remar)c8 have reference to the German mineralogical 
terminology. — ^T. 



Digitized by 



Google 



247 



LI. 

PLANTS. 
617. 

The colours of organic bodies in general may be 
considered as a higher kind of chemical opera- 
tion, for which reason the ancients employed 
the word concoction, T^i^^Sf to designate the 
process. All the elementary colours, as well ad 
the combined and secondary hues, appear on 
the surface of organic productions, while on the 
other hand, the interior, if not colourless, ap- 
pears, strictly speaking, negative when brought 
to the light. As we propose to communicate 
our views respecting organic nature, to a certain 
extent, in another place, we only insert here 
what has been before connected with the doc- 
trine of colours, while it may serve as an intro- 
duction to the further consideration of the views 
alluded to : and first, of plants. 

618. 

Seeds, bulbs, roots, and what is generally shut 
out from the light, or immediately surrounded 
by the earth, appear, for the most part, white. 

619. 

Plants reared from seed, in darkness, are 
white, or approaching to yellow. Light, on the 



Di^itizecADy Google 



248 PLANTS. 

other hand, in acting on their colours, acts at 
the same time on their form. 

620. 

Plants which grow in darkness make, it is 
true, long shoots from joint to joint : but the 
stems between two joints are thus longer than 
they should be; no side stems are produced, 
and the metamorphosis of the plant does not 
take place. 

621. 

Light, on the other hand, places it at once in 
an active state ; the plant appears green, and 
the course of the metamorphosis proceeds unin- 
terruptedly to the period of reproduction. 

622. 

We know that the leaves of the stem are only 
preparations and pre-significations of the in- 
struments of florification and fructification, and 
accordingly we can already see colours in the 
leaves of the stem which, as it were, announce 
the flower from afar, as is the case in the ama- 
ranthus. 

623. 

There are white flowers whose petals have 
wrought or refined themselves to the greatest 
purity ; there are coloured ones, in which the 



Digitized by 



Google 



PLANTS. 249 

elementary hues may be said to fluctuate to and 
fro. There are some which, in tending to the 
higher state, have only partially emancipated 
themselves from the green of the plant. 

624. 

Flowers of the same genus, and even of the 
same kind, are found of all colours. Roses, and 
particularly mallows, for example, vary through 
a great portion of the colorific circle from white 
to yellow, then through red-yellow to bright 
red, and from thence to the darkest hue it can 
exhibit as it approaches blue. 

625. 

Others already begin from a higher degree 
in the scale, as, for example; the poppy, which 
is yellow-red in the first instance, and which 
afterwards approaches a violet hue. 

626. 

Yet the same colours in species, varieties, and 
even in families and classes, if not constant, are 
still predominant, especially the yellow colour : 
blue is throughout rarer. 

627. 

A process somewhat similar takes place in 
the juicy capsule of the fruit, for it increases in 
colour from the green, through the yellowish 



Digitized by 



Google 



250 PLANTS. 

and yellow, up to the highest red, the colour of 
the rind thus indicating the degree of ripeness. 
Some are coloured all round, some only on the 
sunny side, in which last case the augmentation 
of the yellow into red,— the gradations crowd- 
ing in and upon each other, — may be very well 
observed. 

628. 

Maay fruits, too, are coloured internally; 
pure red juices, especially, are common. 

629. 

The colour which is found superficially in the 
flower and penetratingly in the fruit, spreads 
itself through all the remaining parts, colouring 
the roots and the. juices of the stem, and this 
with a very rich and powerful hue. 

630. 

So, again, the colour of the wood passes from 
yellow through the difierent degrees of red up 
to pure red and on to brown. Blue woods are 
unknown to me ; and thus in this degree of or- 
ganisation the active side exhibits itself power- 
ftilly, although both principles appear balanced 
in the general green of the plant. 

631. 
Vfe have seen above that the germ pushing 



Digitized by 



Google 



PLANTS. 261 

from the earth is generally white and yellowish, 
but that by means of the action of light and air 
it acquires a green colour. The same happens 
with young leaves of trees, as may be seen, for 
example, in the birch, the young leaves of which 
are yellowish, and if boiled, yield a beautifiil 
yellow juice : afterwards they become greener, 
while the leaves of other trees become gradually 
blue-green. 

632. 

Thus a yellow ingredient appears to belong 
more essentially to leaves than a blue one ; for 
this last vanishes in the autumn, and the yellow 
of the leaf appears changed to a brown colour. 
Still more remarkable, however, are the parti- 
cular cases where leaves in autumn again be- 
come pure yellow, and others increase to the 
brightest red. 

633. 

Other plants, again, may, by artificial treat- 
ment be entirely converted to a colouring 
matter, which is as fine, active, and infinitely 
divisible as any other. Indigo and madder, 
with which so much is effected, are examples : 
lichens are also used for dyes. , 

634. 
To this fact another stands immediately op- 



Digitized by 



Google 



252 WORMS, INSECTS, FISHES. 

posed; we can, namely, extract the colouring 
part of plants, and, as it were, exhibit it apart, 
while the organisation does not on this account 
appear to suffer at all. The colours of flowers 
may be extracted by spirits of wine, and tinge 
it ; the petals meanwhile becoming white. 

635. 

There are various modes of acting on flowers 
and their juices by re-agents. This has been 
done by Boyle in many experiments. Roses 
are bleached, by sulphur, and may be restored 
to their first state by other acids; roses are 
turned green by the smoke of tobacco. 



LII. 

WORMS, INSECTS, FISHES. 
636. 

With regard to creatures belonging to the lower 
degrees of organisation, we may first observe 
that worms, which live in the earth and remain 
in darkness and cold moisture, are imperfectly 
negatively coloured ; worms bred in warm mois- 
ture and darkness are colourless; light seems 
expressly necessary to the definite exhibition of 
colour. 



Digitized by 



Google 



WORMS, INSECTS, FISHES. 253 

637. 

Creatures which live in water, which, although 
a very dense medium, suffers sufficient light 
to pass through it, appear more or less coloured. 
Zoophytes, which appear to animate the purest 
calcareous earth, are mostly white ; yet we find 
corals deepened into the most beautiful yellow- 
red : in other cells of worms this colour increases 
nearly to bright red. 

638. 

The shells of the crustaceous tribe are beauti- 
fully designed and coloured, yet it is to be re- 
marked that neither land-snails nor the shells 
of Crustacea of fresh water, are adorned with 
such bright colours as those of the sea. 

639. 

In examining shells, particularly such as are 
spiral, we find that a series of animal organs, 
similar to each other, must have moved in- 
creasingly forward, and in turning on an axis 
produced the shell in a series of chambers, divi- 
sions, tubes, and prominences, according to a 
plan for ever growing larger. We remark, how- 
ever, that a tinging juice must have accompanied 
the development of these organs, a juice which 
marked the surface of the shell, probably through 
the immediate co-operation of the sea-water, 
with coloured lines, points, spots, and shadings : 



Digitized by 



Google 



254 WORMS, INSECTS, FISHES. 

this must have taken place at regular intervals, 
and thus left the indications of increasing growth 
lastingly on the exterior ; meanwhile the inte- 
rior is generally found white or only faintly co- 
loured. 

640. 

That such a juice is to be found in shell-fish 
is, besides, sufficiently proved by experience; for 
the creatures furnish it in its liquid and colour- 
ing state: the juice of the ink-fish is an ex- 
ample. But a much stronger is exhibited in the 
red juice found in many shell-fish, which 
was so famous in ancient times, and has been 
employed with advantage by the moderns. 
There is, it appears, in the entrails of many of 
the crustaceous tribe a certain vessel which is 
filled with a red juice; this contains a very 
strong and durable colouring substance, so much 
so that the entire creature may be crushed and 
boiled, and yet out of this broth a sufficiently 
strong tinging liquid may be extracted. But 
the little vessel filled with colour may be sepa- 
rated from the animal, by which means of course 
a concentrated juice is gained. 

641. 

This juice has the property that when ex- 
posed to light and air it appears first yellowish, 
then greenish ; it then passes to blue, then to a 



Digitized by 



Google 



WORMS, INSECTS, FISHES. 255 

violet, gradually growing redder ; and lastly, by 
the action of the sun, and especially if trans- 
ferred to cambric, it assumes a pure bright red 
colour. 

642. 



Digitized by 



Google 



256 WORMS, INSECTS, FISHES. 

wliich takes place by means of breathing. The 
venous blood approaches more to violet, and by 
this mutability denotes the tendency to that 
augmentation and progression which are now 
familiar to us. 

644. 
Before we quit the element whence we de- 
rived the foregoing examples, we may add a few 
observations on fishes, whose scaly surface is 
coloured either altogether in stripes, or in spots, 
and still oftener exhibits a certain iridescent 
appearance, indicating the affinity of the scales 
with the coats of shell-fish, mother-of-pearl, and 
even the pearl itself. At the same time it 
should not be forgotten that warmer climates, 
the influence of which extends to the watery 
regions, produce, embellish, and enhance these 
colours in. fishes in a still greater degree. 

645. 
In Otaheite, Forster observed fishes with 
beautifully iridescent surfaces, and this effect 
was especially apparent at the moment when 
the fish died. We may here call to mind the 
hues of the chameleon, and other similar ap- 
pearances ; for when similar facts are presented 
together, we are better enabled to trace them. 

646. 
Lastly, although not strictly in the same 



Digitized by 



Google 



WORMS, INSECTS, FISHES. 257 

class, the iridescent appearance of certain mo- 
luscae may be mentioned, as well as the phos- 
phorescence which, in some marine creatures^ 
it is said becomes iridescent just before it 
vanishes. 

647. 

We now turn our attention to those creatures 
which belong to light, air and dry warmth, and 
it is here that we first find ourselves in the 
living region of colours. Here, in exquisitely 
organised parts, the elementary colours present 
themselves in their greatest purity and beauty. 
They indicate, however, that the creatures they 
adorn, are still low in the scale of organis- 
ation, precisely because these colours can thus 
appear, as it were, unwrought. Here, too, 
heat seems to contribute much to their develop- 
ment. 

648. 

We find insects which may be considered 
altogether as concentrated colouring matter; 
among these, the cochineals especially are cele- 
brated ; with regard to these we observe that 
their mode of settling on vegetables, and even 
nestling in them, at the same time produces 
those excrescences which are so useful as mor- 
dants in fixing colours. 



Digitized by 



Google 



258 WORMS, INSECTS, FISHES. 

649. 

But the power of colour, accompanied by 
regular organisation, exhibits itself in the most 
Striking manner in those insects which require 
a perfect metamorphosis for their development 
— in scarabaei, and especially in butterflies. 

650. 

These last, which might be called true pro^ 
ductions of light and air, often exhibit the most 
beautifnl colours, even in their chrysalis state, 
indicating the future colours of the butterfly ; a 
consideration which, if pursued further hereafter, 
must undoubtedly afibrd a satisfactory insight 
into many a secret of organised being. 

651. 

If, again, we examine the wings of the but- 
terfly more accurately, and in its net-like web 
discover the rudiments of an arm, and observe 
further the mode in which this, as it were, flat- 
tened arm is covered with tender plumage and 
constituted an organ of flying ; we believe we 
recognise a law according to which the great 
variety of tints is regulated. This will be a 
subject for further investigation hereafter. 

652. 
That, again, heat generally has an influence 



Digitized by 



Google 



BIRDS. 259 



on the size of the creature, on the accomplish- 
ment of the form, and on the greater beauty of 
the colours, hardly needs to be remarked. 



LIII. 

BIRDS. 

653. 

The more we approach the higher organisations, 
the more it becomes necessary to limit ourselves 
to a few passing observations ; for all the natural 
conditions of such organised beings are the re- 
sult of so many premises, that, without having 
at least hinted at these, our remarks would only 
appear daring, and at the same time insufficient. 

654. 

We find in plants, that the consummate 
flower and fruit are, as it were, rooted in the 
stem, and that they are nourished by more per- 
fect juices than the original roots first afibrded ; 
we remark, too, that parasitical plants which 
derive their support from organised structures, 
exhibit themselves especially endowed as to 
their energies and qualities. We might in some 
sense compare the feathers of birds with plants 
of this description ; the feathers spring up as a 
last structural result from the surface of a body 

s2 



Digitized by 



Google 



260 BIRDS. 

which has yet much in reserve for the comple- 
tion of the external economy, and thus are very 
richly endowed organs. 

655. 
The quills not only grow proportionally to a 
considerable size, but are throughout branched, 
by which means they properly become feathers, 
and many of these feathered branches are again 
subdivided ; thus, again, recalling the structure 
of plants. 

666. 
The feathers are very different in shape and 
size, but each still remains the same organ, 
forming and transforming itself according to 
the constitution of the part of the body from 
which it springs. 

667. 
With the form, the colour also becomes 
changed, and a certain law regulates the general 
order of hues as well as that particular dis- 
tribution by which a single feather becomes 
party colouredw It is from this that all com- 
bination of variegated plumage arises^ and 
whence, at last, the eyes in the peacock's tail 
are produced. It is a result similar to that which 
we have already unfolded in treating of the 
metamorphosis of plants, and which we shall 
take an early opportunity to prove. 



Digitized by 



Google 



BIRDS. 2dl 

658. 

Although time aad circumstances compel us 
here to pass by this .organic law, yet we are 
bound to refer to the chemical operations which 
commonly exhibit themselves in the tinting of 
feathers in a mode now sufficiently known to us. 

659. 

Plumage is of all colours, yet, on the whole, 
yellow deepening to red is commoner than blue: 



Digitized by 



Google 



262 
LIV. 

MAMMALIA J^ND HUMAN BEINGS. 
662. 

Herb the elementaiy colours b^in to leave us 
altogether. We are arrived at the highest de- 
gree of the scale, and shall not dwell on its 
characteristics long. 

663. 

An animal of this class is distinguished 
among the examples of organised being. Every 
thing that exhibits itself about him is living. 
Of the internal structure we do not speak» but 
confine ourselves briefly to the surface. The 
hairs are already distinguished from feathers, 
inasmuch as they belong more to the skin, in* 
asmuch as they are simple, thread-like, not 
branched. They are however, like feathers, 
shorter, longer, softer, and firmer, colourless 
or coloured, and all this in conformity to laws 
which might be defined. 

664. 

White and black, yellow, yellow-red and 
brown, alternate in various modifications, but 
they never appear in such a state as to remind 
us of the elementary hues. On the contrary. 



Digitized by 



Google 



MAMMALIA AND HUMAN BEINGS. 263 

they are all broken colours subdued by organic 
concoction, and thus denote, more or less, the 
perfection of life in the being they belong to. 

665- 
One of the most important considerations con- 
nected with morphology, so far as it relates to 
surfaces, is this, that even in quadrupeds the 
spots of the skin have a relation with the parts 
underneath them. Capriciously as nature here 
appears, on a hasty examination, to operate, she 
nevertheless consistently observes a secret law. 
The development and application of this, it is 
true, are reserved only for accurate and careful 
investigation and sincere co-operation. 

666. 
If in some animals portions appear variegated 
with positive colours, this of itself shows how 
far such creatures are removed from a perfect 
organisation ; for, it may be said, the nobler a 
creature is, the more all the mere material of 
which he is composed, is disguised by being 
wrought together ; the more essentially his sur« 
face corresponds with the internal organisation, 
the less can it exhibit the elementary colours. 
Where all tends to make up a perfect whole, 
any detached specific developments cannot take 
place. 

667. 

Of man we have little to say, for he is en- 

i 



Digitized by 



Google 



264 MAMMALIA AND HUMAN BEINGS. 

tirely distinct from the general physiological 
results of which we now treat. So much in this 
case is in affinity with the internal structure, 
that the surface can only be sparingly endowed. 

668. 

When we consider that brutes are rather en- 
cumbered than advantageously provided with 
intercutaneous muscles ; when we see that 
much that is superfluous tends to the surface, 
as, for instance, large ears and tails, as well as 
hair, manes, tufts ; we see that nature, in such 
cases, had much to give away and to lavish. 

669. 

On the contrary, the general surface of the 
human form is smooth and clean, and thus in 
the most perfect examples, the beautiful forms 
are apparent ; for it may be remarked in pass- 
ing, that a superfluity of hair on the chest, arms, 
and lower limbs, rather indicates weakness than 
strength. Poets only have sometimes been in- 
duced, probably by the example of the ferine 
nature, so strong in other respects, to extol 
similar attributes in their rough heroes. 

670. 

But we have here chiefly to speak of colour, 
and observe that the colour of the human skin, 
in all its varieties, is never an elementary co- 



Digitized by 



Google 



MAMMALIA AND HUMAN BEINGS. 205 

lour, but presents^ by means of organic concoc- 
tion, a highly complicated result. — Note X. 

671. 

That the colour of the skin and hair has rela- 
tion with the differences of character^ is beyond 
question ; and we are led to conjecture that the 
circumstance of one or other organic system 
predominating, produces the varieties we see. 
A similar hypothesis may be applied to nations, 
in which case it might perhaps be observed, that 
certain colours correspond with certain confirm- 
ations, which has always been observed of the 
negro physiognomy. 

672. 

Lastly, we might here consider the problem- 
atical question, whether all human forms and 
hues are not equally beautiful, and whether 
custom and self-conceit are not the causes why 
one is preferred to another? We venture, how- 
ever, after what has been adduced, to assert that 
the white man, that is, he whose surface varies 
from white to reddish, yellowish, brownish, in 
short, whose surface appears most neutral in 
hue and least inclines to any particular or 
positive colour, is the most beautiful. On the 
same principle a similar point of perfection in 
human conformation may be defined hereafter, 
when the question relates to form. We do not 



Digitized by 



Google 



266 PHYSICAL AND CHEMICAL SFFBCT8 OF 

imagine that this long-disputed question is to be 
thus, once for all, settled, for there are persons 
enough who have reason to leave this significancy 
of the exterior in doubt ; but we thus express a 
conclusion^ derived from observation and reflec- 
tion, such as might suggest itself to a mind 
aiming at a satisfactory decision. We subjoin 
a few observations connected with the elemen- 
tary chemical doctrine of colours* — Note Y. 



LV. 

PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMIS- 
SION OF LIGHT THROUGH COLOURED MEDIUMS. 

673. 

The physical and chemical effects of colourless 
light are known, so that it is unnecessary here 
to describe them at length. Colourless light 
exhibits itself under various conditions as ex- 
citing warmth, as imparting a luminous quality 
to certain bodies, as promoting oxydation and 
de-oxydation. In the modes and d^rees of 
these effects many varieties take place, but no 
difference is found indicating a principle of 
contrast such as we find in the transmission of 
coloured light. We proceed briefly to advert to 
this. 



Digitized by 



Google 



LIGHT THROUGH COLOURED MEDIUMS. 267 

674. 

Let the temperature of a dark room be ob- 
served by means of a very sensible air-thermo- 
meter; if the bulb is then brought to the direct 
sun light as it shines into the room, nothing is 
more natural than that the fluid should indicate 
a much higher degree of warmth. If upon this 
we interpose coloured glasses, it follows again 
quite naturally that the degree of warmth must 
be lowered ; first, because the operation of the 
direct light is already somewhat impeded by 
the glass, and again, more especially, because a 
coloured glass, as a dark medium, admits less 
light through it. 

675. 

But here a difference in the excitation of 
warmth exhibits itself to the attentive observer, 
according to the colour of the glass. The yel- 
low and the yellow-red glasses produce a higher 
temperature than the blue and blue-red, the 
difference being considerable. 

676. 

This experiment may be made with the pris- 
matic spectrum. The temperature of the room 
being first remarked on the thermometer, the 
blue coloured light is made to fall on the bulb, 
when a somewhat, higher degree of warmth is 
exhibited, which still increases as the other co? 



Digitized by 



Google 



268 PHYSICAL AND CHEMICAL EFFECTS OF 

lours are gradually brought to act on the mer- 
cury. If the experiment is made with the water- 
prism, so that the white light can be retained in 
the centre, this, refracted indeed, but not yet co- 
loured light, is the warmest ; the other colours, 
stand in relation to each other as before* 

677. 

As we here merely describe, without under- 
taking to deduce or explain this phenomenon, 
we only remark in passing, that the pure light is 
by no means abruptly and entirely at an end 
with the red division in the spectrum, but that 
a refracted light is still to be observed deviating 
from its course and, as it were, insinuating itself 
beyond the prismatic image, so that on closer 
examination it will hardly be found necessary 
to take refuge in invisible rays and their refrac- 
tion. 

678. 

The communication of light by means of co- 
loured mediums exhibits the same difference. 
The light communicates itself to Bologna phos- 
phorus through blue and violet glasses, but by 
no means through yellow and yellow-red glasses. 
It has been even remarked that the phosphori 
which have been rendered luminous under violet 
and blue glasses, become sooner extinguished 
when afterwards placed under yellow and yel- 
low-red glasses than those which have been 



Digitized by 



Google 



f 

LIGHT THROUGH COLOURSD MEDIUMS. 269 

suffered to remain in a dark room without any 
further influence. 

679. 

These experiments, like the foregoing, may 
also be made by means of the prismatic spec- 
trum, when the same results take place. 

680. 

To ascertain the effect of coloured light on 
oxydation and de-oxydation, the following means 
may be employed : — Let moist, perfectly white 
muriate of silver* be spread on a strip of paper; 
place it in the lights so that it may become to a 
certain degree grey, and then cut it in three 
portions. Of these, one may be preserved in a 
book, as a specimen of this state ; let another 
be placed under a yellow-red, and the third 
under a blue-red glass. The last will become a 
darker grey, and exhibit a de-oxydation ; the 
other, under the yellow-red glass, will, on the 
contrary, become a lighter grey, and thus ap- 
proach nearer to the original state of more per- 
fect oxydation. The change in both may be 
ascertained by a comparison with the unaltered 
specimen. 

681. 
An excellent apparatus has been contrived to 

* Now generally called chloride of silver: the term in the 
original is Homsilber.— T. 



Digitized by 



Google 



270 CHEMICAL EFFECT IN 

perform these experiments with the prismatic 
image. The results are analogous to those al- 
ready mentioned, and we shall hereafter give 
the particulars, making use of the labours of an 
accurate observer, who has been for some time 
carefully prosecuting these experiments.* 



LVI. 

CHEMICAL EFFECT IlT DIOPTRICAL ACHROMATISM. 
682. 

We first invite our readers to turn to what has 
been before observed on this subject (285. 298), 
to avoid unnecessary repetition here. 

683. 

We can thus give a glass the property of 
producing much wider coloured edges without 
refracting more strongly than before^ that is, 
without displacing the object much more per- 
ceptibly. 

684. 

This property is communicated to the glass 
by means of metallic oxydes. Minium, melted 
and thoroughly united with a pure glass, pro- 

* The individual alluded to wae Seebeck : the result of hit ex- 
periments was published in the second volume. — ^T. 



Digitized by 



Google 



DIOPTRICAL ACHROMATISM. 271 

duces this effect, and thus flint-glass (291) is 
prepared with oxyde of lead. Experiments of 
this kind have been carried farther, and the so- 
called butter of antimony^ which, according to 
a new preparation, may be exhibited as a pure 
fluid, has been made use of in hollow lenses 
and prisms, producing a very strong appearance 
of colour with a very moderate refraction, and 
presenting the eflect which we have called hy^ 
perchromatism in a very vivid manner. 

686. 

In common glass, the alkaline nature ob- 
viously preponderates, since it is chiefly com- 
posed of sand and alkaline salts ; hence a series 
of experiments, exhibiting the relation of per- 
fectly alkaline fluids to perfect acids, might lead 
to useful results. 

686. 

For, could the maximum and minimum be 
found, it would be a question whether a refract- 
ing medium could not be discovered, in which 
the increasing and diminishing appearance of 
colour, (an effect almost independent of refrac- 
tion,) could not be done away with altogether, 
while the displacement of the object would be 
unaltered. 

687. 
How desirable, therefore, it would be with 



Digitized by 



Google 



272 GENERAL REFLECTIONS. 

regard to this last point, as well as for the elu- 
cidation of the whole of this third division of 
our work, and^ indeed, for the elucidation of the 
doctrine of colours generally, that those who are 
occupied in chemical researches, with new views 
ever opening to them, should take this subject 
in hand, pursuing into more delicate combina- 
tions what we have only roughly hinted at, and 
prosecuting their inquiries with reference to 
science as a whole. 



Digitized by 



Google 



273 



PART IV. 

GENERAL CHAaACTEBISTICS. 

688. 

We have hitherto, in a manner forcibly, kept 
phenomena asunder, which, partly from their 
nature, partly in accordance with our mental 
habits, have, as it were, constantly sought to be 
reunited. We have exhibited them in three 
divisions. We have considered colours, first, as 
transient, the result of an action and re-action 
in the eye itself; next, as passing effects of 
colourless, light-transmitting, transparent, or 
opaque mediums on light; especially on the 
luminous image ; lastly, we arrived at the point 
where we could securely pronounce them as 
permanent, and actually inherent in bodies. 

689. 

In following this order we have as far as pos^ 
sible endeavoured to define, to separate, and to 
class the appearances. But now that we need 
no longer be apprehensive of mixing or con^ 
founding them, we may proceed, first, to state 
the general nature of these appearances con- 
Bidered abstractedly, as an independent circle 
of facts, and, in the next place, to show how 
this particular circle is connected with other 
classes of analogous phenomena in nature. 



Digitized by 



Google 



274 

THE FACILITY WITH WHICH COLOUR APPEARS. 
690. 

We have observed that colour under many 
conditions appears very easily. The suscep- 
tibility of the eye with regard to light, the 
constant re-action of the retina against it, pro- 
duce instantaneously a slight iridescence. 
Every subdued light may be considered as 
coloured, nay, we ought to call any light coloured, 
inasmuch as it is seen. Colourless light, colour- 
less surfaces, are, in some sort, abstract ideas ; 
in actual experience we can hardly be said to be 
aware of them. — Note Z. 

691. 

If light impinges on a colourless body, is re- 
flected from it or passes through it, colour im- 
mediately appears ; but it is necessary here to 
remember what has been so often urged by us, 
namely, that the leading conditions of refrac- 
tion, reflection, &c., are not of themselves sufii- 
cient to produce the appearance. Sometimes, 
it is true, light acts with these merely as light, 
but oftener as a defined, circumscribed appear- 
ance, as a luminous image. The semi-opacity 
of the medium is often a necessary condition ; 
while half, and double shadows, are required 
for many coloured appearances. In all casea^ 
however, colour appears instantaneously. We 
find, again, that by means of pressure, breathing 
heat (432, 471), by various kinds of motion and 



Digitized by 



Google 



THE FOBCE OF COLOUR. 276 

alteration on smooth clean surfaces (461) » as 
well as on colourless fluids (470), colour is im- 
mediately produced. 

692. 

The slightest change has only to take place 
in the component parts of bodies^ whether by 
immixture with other particles or other such 
efiects, and colour either makes its appearance 
or becomes changed. 

THE FOBCE OF COLOUR. 

693. 

The physical colours, and especially those of 
the prism, were formerly called ^'colores em^ 
phatici,^' on account of their extraordinary 
beauty and force. Strictly speaking, however, 
a high degree of efiect may be ascribed to all 
appearances of colour, assuming that they are 
exhibited under the purest and most perfect 
conditions. 

694. 

The dark nature of colour, its full rich quality, 
is what produces the grave, and at the same 
time fascinating impression we sometimes ex- 
perience, and as colour is to be considered a 
condition of light, so it cannot dispense with 
light as the co-operating cause of its appear- 
ance, as its basis or ground ; as a power thus 
displaying and manifesting colour. 

T 2 



Digitized by 



Google 



27fl 

THE DEFINITE NATUBE OF COLOUB. 
695. 

The existence and the relatively definite cha- 
racter of colour are one and the same thing. 
Light displays itself and the face of nature, as 
it were, with a general indifference, informing 
us as to surrounding objects perhaps devoid of 
interest or importance ; but colour is at all times 
specific, characteristic, significant. 

696. 
Considered in a general point of view, colour 
is determined towards one of two sides. It thus 
presents a contrast which we call a polarity, 
and which we may fitly designate by the ex- 
pressions phis and minus. 



Plus. 


Minus, 


Yellow. 


Blue. 


Action. 


Negation.* 


T-ight. 


Shadow. 


Brightness. 


Darkness. 


Force. 


Weakness. 


Warmth. 


Coldness. 


Proximity. 


Distance. 


Repulsion 


Attraction. 


Affinity with acids ^ 


Affinity with alkalis. 



* Wirkung, fieraubung; the last would be more literally ren- 
dered privation. The author has already frequently made use of 
the terms active and passive as equivalent to plus and mtnia.-^T. 



Digitized by 



Google 



277 



COMBINATION OF THE TWO PRINCIPLES. 
697. 

If these specific, contrasted principles are 
combined, the respective qualities do not there- 
fore destroy each other : for if in this intermix- 
ture the ingredients are so perfectly balanced that 
neither is to be distinctly recognised, the union 
again acquires a specific character ; it appears 
as a quality by itself in which we no longer 
think of combination. This union we call green. 

698. 

Thus, if two opposite phenomena springing 
from the same source do not destroy each other 
when combined, but in their, union present a 
third appreciable and pleasing appearance, this 
result at once indicates their harmonious rela- 
tion. The more perfect result yet remains to be 
adverted to. 

AUGMENTATION TO RED. 

699. 
Blue and yellow do not admit of increased 
intensity without presently exhibiting a new 
appearance in addition to their own. Each 
colour, in its lightest state, is a dark ; if con- 
densed it must become darker, but this efiect no 
sooner takes place than the hue assumes an 
appearance which we designate by the word 
reddish. 



Digitized by 



Google 



278 AUGMENTATION TO EED. 

700. 

This appearance still increases, so that when 
the highest degree of intensity is attained it 
predominates over the original hue. A powerful 
impression of light leaves the sensation of red 
on the retina. In the prismatic yellow-red 
which springs directly from the yellow, we 
hardly recognise the yellow. 

701. 

This deepening takes place again by means of 
colourless semi-transparent mediums, and here 
we see the effect in its utmost purity and ex* 
tent. Transparent fluids, coloured with any 
given hues, in a series of glass-vessels, exhibit 
it very strikingly. The augmentation is unre- 
mittingly rapid and constant; it is universal, 
and obtains in physiological as well as in phy- 
sical and chemical colours. 

JUNCTION OP THE TWO AUGMENTED EXTREMES. 
702. 

As the extremes of the simple contrast pro- 
duce a beautiful and agreeable appearance by 
their union, so the deepened extremes on being 
united, will present a still more fascinating 
colour ; indeed, it might naturally be expected 
that we should here find the acme of the whole 
phenomenon. 



Digitized by 



Google 



C0MPLETENB8S THE RESULT OF VARIETY. 279 
703. 

And such is the fact, for piire red appears ; a 
colour to which, from its excellence, we have 
appropriated the term ** purpur."* 

704. 

There are various modes in which pure red 
may appear. By bringing together the violet 
edge and yellow-red border in prismatic experi- 
ments, by continued augmentation in chemical 
operations* and by the organic contrast in phy- 
siological effects. 

705. 

As a pigment it cannot be produced by inter- 
mixture or union, but only by arresting the hue 
in substances chemically acted on, at the high 
culminating point. Hence the painter is jus- 
tified in assuming that there are three primitive 
colours from which he combines all the others. 
The natural philosopher, on the other hand, 
assumes only two elementary colours, from which 
he, in like manner, developes and combines the 
rest. 

COHPLETENESS THE RESULT OF VARIETY IN COLOUR. 

706. 

The various appearances of colour arrested in 

♦ Wherever this word occurs incidentally it is translated pure 
red^ the English word purple being generally employed to denote 
a colour similar to violet. — ^T. 



Digitized by 



Google 



280 HARMONY OF THE COMPLETE STATE. 

their different degrees, and seen in juxtaposi- 
tion, produce a whole. This totality is harmony 
to the eye. 

707. 
The chromatic circle has been gradually pre- 
sented to us ; the various relations of its pro- 
gression are apparent to us. Two pure original 
principles in contrast, are the foundation of the 
whole ; an augmentation manifests itself by 
means of which both approach a third state ; 
hence there exists on both sides a lowest and 
highest, a simplest and most qualified state. 
Again, two combinations present themselves; 
first that of the simple primitive contrasts, then 
that of the deepened contrasts. 

HARMONY OF THE COMPLETE STATE. 
703. 

The whole ingredients of the chromatic scale, 
seen in juxtaposition, produce an harmonious 
impression on the eye. The difference between 
the physical contrast and harmonious opposition 
in all its extent should not be overlooked. The 
first resides in the pure restricted original dual- 
ism, considered in its antagonizing elements; 
the other results from the the fully developed 
effects of the complete state. 

709. 
Every single opposition in order to be har- 
monious must comprehend the whole. The 



Digitized by 



Google 



EVANESCENCE OF COLOUR. 281 

physiological experiments are sufficiently con- 
vincing on this point. A development of all the 
possible contrasts of the chromatic scale will be 
shortly given* 

FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND 
EITHER TO THE PLUS OR MINUS SIDE. 

710. 

We have already had occasion to take notice 
of the mutability of colour in considering its so- 
called augmentation and progressive variations 
round the whole circle ; but the hues even pass 
and repass from one side to the other, rapidly 
and of necessity. 

711. 
Physiological colours are different in appear- 
ance as they happen to fall on a dark or on a 
light ground. In physical colours the combina- 
tion of the objective and subjective experiments 
is very remarkable. The epoptical colours, it 
appears, are. contrasted according as the light 
shines through or upon them. To what extent 
the chemical colours may be changed by fire 
and alkalis, has been sufficiently shown in its 
proper place. 

EVANESCENCE OF COLOUR, 

712. 
All that has been adverted to as subsequent 

* No diagram or table of this Iqnd was ever given by the au- 
thor.— T. 



Digitized by 



Google 



282 PERMANENCE OF COLOUR. 

to the rapid excitation and definition of colour, 
immixture, augmentation, combination, separa- 
tion, not forgetting the law of compensatory 
harmony, all takes place with the greatest 
rapidity and facility ; but with equal quickness 
colour again altogether disappears. ' 

7ia. 

The physiological appearances are in no wise 
to be arrested ; the physical last only as long as 
the external condition lasts ; even the chemical 
colours have great mutability, they may be 
made to pass and repass fix>m one side to the 
other by means of opposite re-agents, and may 
even be annihilated altogether. 

PERMANENCE OF COLOUR. 

714. 

The chemical colours afford evidence of very 
great duration. Colours fixed in glass by 
fusion, and by nature in gems, defy all time and 
re-action. 

716. 

The art of dyeing again fixes colour very 
powerfully. The hues of pigments which might 
otherwise be easily rendered mutable by re- 
agents, may be communicated to substances in 
the greatest permanency by means of mordants. 



Digitized by 



Google 



283 



PART V. 

RELATION TO OTHER PURSUITS— RELATION TO 
PHILOSOPHY. 



Digitized by 



Google 



284 RELATION TO PHILOSOPHY. 

718. 

We have before (175) alluded to this im- 
portant consideration, and repeat it here where 
it is in its place. The worst that can happen to 
physical science as well as to many other kinds 
of knowledge is, that men should treat a se- 
condary phenomenon as a primordial one, and 
(since it is impossible to derive the original fact 
from the secondary state), seek to explain what 
is in reality the cause by an effect made to 
usurp its place. Hence arises an endless con- 
fusion, a mere verbiage, a constant endeavour to 
seek and to find subterfuges whenever truth 
presents itself and threatens to be overpowering. 

719. 

While the observer, the investigator of nature, 
is thus dissatisfied in finding that the appear- 
ances he sees still contradict a received theory, 
the philosopher can calmly continue to operate 
in his abstract department on a false result, for 
no result is so false but that it can be made to 
appear valid, as form without substance, by 
some means or other. 

720. 

If, on the other hand, the investigator of na- 
ture can attain to the knowledge of that which 
we have called a primordial phenomenon, he is 
safe ; and the philosopher with him. The inves- 



Digitized by 



Google 



RELATION TO PHILOSOPHY. 286 

tigator of nature is safe^ since he is persuaded 
that he has here arrived at the limits of his 
science, that he finds himself at the height of 
experimental research ; a height whence he can 
look back upon the details of observation in all 
its steps, and forwards into, if he cannot enter, 
the regions of theory. The philosopher is safe, 
for he receives from the experimentalist an 
ultimate fact, which, in his hands, now becomes 
an elementary one. He now justly pays little 
attention to appearances which are understood 
to be secondary, whether he already finds them 
scientifically arranged, or whether they present 
themselves to his casual observation scattered 
and confused. Should he even be inclined to 
go over this experimental ground himself, and 
not be averse to examination in detail, he does 
this conveniently, instead of lingering too long 
in the consideration of secondary and inter- 
mediate circumstances, or hastily passing them 
over without becoming accurately acquainted 
with them. 

721. 

To place the doctrine of colours nearer, in this 
sense, within the philosopher's reach, was the 
author's wish ; and although the execution of 
his purpose, firom various causes, does not cor- 
respond with his intention, he will still keep 
this object in view in an intended recapitula-^ 



Digitized by 



Google 



286 RELATION TO MATHEMATICS. 

tion, as well as in the polemical and historical 
j>ortions of his work ; for he will have to return 
to the consideration of this -point hereafter, on 
an occasion where it will be necessary to speak 
with less reserve. 

RELATION TO MATHEMATICS. 

722. 

It may be expected that the investigator of 
nature, who proposes to treat the science of 
natural philosophy in its entire range, should 
be a mathematician. In the middle ages, ma- 
thematics was the chief organ by means of 
which men hoped to master the secrets of nature, 
and even now, geometry in certain department& 
of physics, is justly considered of first import- 
ance. 

723. 

The author can boast of no attainments of 
this kind, and on this account confines himself 
to departments of science which are indepen- 
dent of geometry; departments which in mo- 
dem times have been opened up far and wide. 

724. 

It will be universally allowed that mathema- 
tics, one of the noblest auxiliaries which can 
be employed by man, has, in one point of view, 
been of the greatest use to the physical sciences; 
but that, by a false application of its methods, 



Digitized by 



Google 



RELATION TO MATHEMATICS. 287 

it has, in many respects, been prejudicial to 
them, is also not to be denied ; we find it here 
and there reluctantly admitted. 

725. 

The theory of colours, in particular, has suf- 
fered much, and its progress has been incalcu- 
lably retarded by having been mixed up with: 
optics generally, a science which cannot dis- 
pense with mathematics; whereas the theory of 
colours, in strictness, may be investigated quite 
independently of optics. 



Digitized by 



Google 



288 RELATION TO MATHEMATICS. 

quainted, been prevented by other occupations 
from making common cause with him, his work 
would not have wanted some merit in this re- 
spect. But this very want may be in the end ad- 
vantageous, since it may now become the object 
of tlie enlightened mathematician to ascertain 
where the doctrine of colours is in need of his 
aid, and how he can contribute the means at 
his command with a view to the complete eluci* 
dation of this branch of physics. 

728. 

In general it were to be wished that the Ger- 
mans^ who render such good service to science, 
while they adopt all that is good from other 
nations, could by degrees accustom themselves 
to work in concert. We live, it must be con- 
fessed, in an age, the habits of which are directly 
opposed to such a wish. Every one seeks, not 
only to be original in his views, but to be inde- 
pendent of the labours of others, or at least to 
persuade himself that he is so, even in the course 
of his life and occupation. It is very often re- 
marked that men who undoubtedly have accom- 
plished much, quote themselves only, their own 
writings, journals, and compendiums ; whereas 
it would be far more advantageous for the indi- 
vidual, and for the world, if many were devoted 
to a common pursuit. The conduct of our 
neighbours the French is, in this respect, worthy 



Digitized by 



Google 



TECHNICAL OPERATIONS OF THE DYER. 289 

of imitation; we have a pleasing instance in 
Cuvier's preface to his ''Tableau E16mentaire 
de THistoire Naturelle des Animaux." 

729. 

He who has observed science and its pro- 
gress with an unprejudiced eye, might even ask 
whether it is desirable that so many occupa- 
tions and aims, though allied to each other, 
should be united in one person, and whether it 
would not be more suitable for the limited 
powers of the human mind to distinguish, for 
example, the investigator and inventor, from 
him who employs and applies the result of ex- 
periment? Astronomers, who devote themselves 
to the observation of the heavens and the disco- 
very or enumeration of stars, have in modern 
times formed, to a certain extent, a distinct 
class from those who calculate the orbits, con- 
sider the universe in its connexion, and more 
accurately define its laws. The history of the 
doctrine of colours will often lead us back to 
these considerations. 

RELATION TO THE TECHNICAL OPERATIONS OF 
THE DYER. 

730. 

If in our labours we have gone out of the 
province of the mathematician, we have, on the 
other hand, endeavoured to meet the practical 



Digitized by 



Google 



290 TECHNICAL OPERATIONS OF THE DYER. 

views of the dyer; and although the chapter 
which treats of colour io a chemical point of 
view is not the most complete and circumstan- 
tial, yet in that portion, as well as in our general 
observations respecting colour, the dyer will find 
his views assisted far more than by the theory 
hitherto in vogue, which failed to afibrd him 
any assistance. 

731. 

It is curious, in this view, to take a glance 
at the works containing directions on the art of 
dyeing. As the Catholic, on entering his tem- 
ple, sprinkles himself with holy water, and after 
bending the knee, proceeds perhaps to converse 
with his friends on his affairs, without any espe^ 
cial devotion ; so all the treatises on dyeing 
begin with a respectful allusion to the accre^ 
dited theory, without afterwards exhibiting a 
single trace of any principle deduced from this 
theory, or showing that it has thrown light on 
any part of the art, or that it offers any useful 
hints in furtherance of practical methods. 

732. 

On the other hand, there are men who, after 
having become thoroughly and experimentally 
acquainted with the nature of dyes, have not 
been able to reconcile their observations with 
the received theory ; who have, in short, disco- 



Digitized by 



Google 



RELATION TO PHYSIOLOGY AND PATHOLOGY. 291 

vered its weak points^ and sought for a general 
view more consonant to nature and experience. 
When we come to the names of Castel and 
Giilich, in our historical review, we shall have 
occasion to enter into this more fully, and an 
opportunity will then present itself to show that 
an assiduous experience in taking advantage of 
every accident may, in fact, be said almost to 
exhaust the knowledge of the province to which 
it is confined. The high and complete result is 
then submitted to the theorist, who, if he ex- 
amines facts with accuracy, and reasons with 
candour, will find such materials eminently 
useful as a basis for his conclusions. — Note A A. 

RELATION TO PHYSIOLOGY AND PATHOLOGY. 
733. 

If the phenomena adduced in the chapter 
where colours were considered in a physiological 
and pathological view are for the most part 
generally known, still some new views, mixed 
up with them, will not be unacceptable to the 
physiologist. We especially hope to have given 
him cause to be satisfied by classing certain 
phenomena which stood alone, under analogous 
facts, and thus, in some measure, to have pre- 
pared the way for his further investigations. 

734. 
The appendix on pathological colours, again, 

u 2 



Digitized by 



Google 



292 RELATION TO NATURAL HISTORY. 

is admitted to be scanty and unconnected. We 
reflect, however, that Germany can boast of 
men who are not only highly experienced in 
this department, but are likewise so distin- 
guished for general cultivation, that it can cost 
them but little to revise this portion, to com- 
plete what has been sketched, and at the same 
time to connect it with the higher facts of 
organisation. 

RELATION TO NATURAL HISTORY. 
735. 

If we may at all hope that natural history 
will gradually be modified by the principle of 
deducing the ordinary appearances of nature 
from higher phenomena, the author believes he 
may have given some hints and introductory 
views bearing on this object also. As colour, 
in its infinite variety, exhibits itself on the sur- 
face of living beings, it becomes an important 
part of the outward indications, by means of 
which we can discover what passes underneath. 

736. 

In one point of view it is certainly not to be 
too much relied on, on account of its indefinite 
and mutable nature; yet even this mutability, 
inasmuch as it exhibits itself as a constant qua- 
lity, again becomes a criterion of a mutable 
vitality ; and the author wishes nothing more 



Digitized by 



Google 



Digitized by 



Google 



294 RELATION TO GENERAX PHYSICS. 

indicate an original division which is capable 
of union, or an original unity which admits of 
division, and that the phenomenon will present 
itself accordingly. To divide the united, to 
unite the divided, is the life of nature ; this is 
the eternal systole and diastole,* the eternal col- 
lapsion and expansion, the inspiration and 
expiration of the world in which we live and 
move. 

740. 

It is hardly necessary to observe that what we 
here express as number and restrict to dualism 
is to be understood in a higher sense; the ap- 
pearance of a third, a fourth order of facts pro- 
gressively developing themselves is to be simi- 
larly understood; but actual observation should, 
above all, be the basis of all these expressions. 

741. 

Iron is known to us as a peculiar substance, 
different froiri other substances : in its ordinary 
state we look upon it as a mere material remark- 
able only on account of its fitness for various 
uses and applications. How little, however, is 
necessary to do away with the comparative insig- 
nificancy of this substance. A two-fold power is 
called forth,* which, while it tends again to a 

* Eine Entzweyung geht vor ; literally, a division takes place. 
According to some, the two magnetic powers are previously in 
the bar, and are then separated at the ends. — T. 



Digitized by 



Google 



RELATION TO GENERAL PHYSICS. 295 

8tate of union, and, as it were, seeks itself, ac- 
quires a kind of magical relation with its like, 
and propagates this double property, which is 
in fact but a principle of reunion, throughout 
all bodies of the same kind. We here first ob- 
serve the mere substance, iron ; we see the divi- 
sion that takes place in it propagate itself and 
disappear, and again easily become re-excited. 
This, according to our mode of thinking, is a 
primordial phenomenon in immediate relation 
with its idea, and which acknowledges nothing 
earthly beyond it. 

742. 

Electricity is again peculiarly characterised. 
As a mere quality we are unacquainted with it; 
for us it is a nothing, a zero, a mere point, which, 
however, dwells in all apparent existences, and 
at the same time is the point of origin whence, 
on the slightest stimulus, a double appearance 
presents itself, an appearance which only mani- 
fests itself to vanish. The conditions under 
which this manifestation is excited are infinitely 
varied, according to the nature of particular 
bodies. From the rudest mechanical friction c>f 
very different substances with one another, to 
the mere contiguity of two entirely similar bo- 
dies, the phenomenon is present and stirring, 
nay, striking and powerful, and so decided and 
specific, that when we employ the terms or for- 



Digitized by 



Google 



296 RELATION TO GENERAL PHYSICS. 

mulse polarity, plus and minus, for north and 
south, for glass and resin, we do so justifiably 
and in conformity with nature. 

743. 
This phenomenon, although it especially af- 
fects the surface, is yet by no means superficial. 
It influences the tendency or determination of 
material qualities^ and connects itself in imme- 
diate co-operation with the important double 
phenomenon which takes place so universally 
in chemistry^ — oxydation, and de-oxydation. 

744. 
To introduce and include the appearances of 
colour in this series, this circle of phenomena 
was the object of our labours. What we have 
not succeeded in others will accomplish. We 
found a primordial vast contrast between light 
and darkness, which may be more generally 
expressed by light and its absence. We looked 
for the intermediate state, and sought by means 
of it to compose the visible world of light, 
shade, and colour. In the prosecution of this 
we employed various terms applicable to the 
development of the phenomena, terms which 
we adopted from the theories of magnetism, of 
electricity, and of chemistry. It was necessary, 
however, to extend this terminology, since we 
found ourselves in an abstract region, and had 
to express more complicated relations. 



Digitized by 



Google 



RELATION TO GENERAL PHYSICS. 297 

745. 

If electricity and galvanism, in their general 
character, are distinguished as superior to the 
more limited exhibition of magnetic phenomena, 
it may be said that colour, although coming 
under similar laws, is still superior ; for since 
it addresses itself to the noble sense of vision, 
its perfections are more generally displayed. 
Compare the varied effects which result from 
the augmentation of yellow and blue to red, 
from the combination of these two higher ex- 
tremes to pure red, and the union of the two 
inferior extremes to green. What a far more 



Digitized by 



Google 



298 RELATION TO THE THEORY OF MUSIC. 

science, technical processes, and art, if it should 
prove possible to rescue the attractive subject 
of the doctrine of colours from the atomic re- 
striction and isolation in which it has been 
banished, in order to restore it to the general 
dynamic flow of life and action which the pre- 
sent age loves to recognise in nature. These 
considerations will press upon us more strongly 
when, in the historical portion, we shall have to 
speak of many an enterprising and intelligent 
man who failed to possess his contemporaries 
with his convictions. 

RELATION TO THE THEORY OF MUSIC. 

747. 

Before we proceed to the moral associations 
of colour, and the aesthetic influences arising 
from them, we have here to say a few words on 
its relation to melody. That a certain relation 
exists between the two, has been always felt ; 
this is proved by the frequent comparisons we 
meet with, sometimes as passing allusions, 
sometimes as circumstantial parallels. The 
error which writers have fallen into in trying to 
establish this analogy we would thus define : 

748. 

Colour and sound do not admit of being di- 
rectly compared together in any way, but both 
are referable to a higher formula, both are de- 



Digitized by 



Google 



RELATION TO THE THEORY OF MUSIC. 299 

rivable, although each for itself, from this higher 
law. They are like two rivers which have their 
source. in one and the same mountain, but sub- 
sequently pursue their way under totally dif- 
ferent conditions inr two totally different regions, 
so that throughout the whole course of both no 
two points can be compared. Both are general, 
elementary effects acting according to the gene- 
ral law of separation and tendency to union, of 
undulation and oscillation, yet acting thus in 
wholly different provinces, in different modes. 



Digitized by 



Google 



300 CONCLUDING OBSERVATIONS ON TERMINOLOGY. 

mathematical, aesthetical influences — and to 
substitute for all this a merely physical inquiry 
tending to resolve the science into its first ele- 
ments. Yet considering the point at which 
science and art are now arrived, considering the 
many excellent preparatory investigations that 
have been made relative to this subject, we may 
perhaps still see it accomplished. 

CONCLUDING OBSERVATIONS ON TERMINOLOGY. 

751. 
We never sufficiently reflect that a language, 
strictly speaking, can only be symbolical and 
figurative, that it can never express things di- 
rectly, but only, as it were, reflectedly. This 
is especially the case in speaking of qualities 
which are only imperfectly presented to obser- 
vation, which might rather be called powers 
than objects, and which are ever in movement 
throughout nature. They are not to be arrested, 
and yet we find it necessary to describe them ; 
hence we look for all kinds of formulae in order, 
figuratively at least, to define them. 

752. 
Metaphysical formulae have breadth as well 
as depth, but on this very account they require 
a corresponding import; the danger here is 
vagueness. Mathematical expressions may in 
many cases be very conveniently and happily 



Digitized by 



Google 



CONCLUDING OBSERVATIONS ON TERMINOLOGY. 301 

employed, but there is always an inflexibility 
in them, and we presently feel their inadequacy; 
for even in elementary cases we are very soon 
conscious of an incommensurable idea; they 
are, besides, only intelligible to those who are 
especially conversant in the sciences to which 



Digitized by 



Google 



302 CONCLUDING 0B8ERTATI0NS ON TERMINOLOGY. 

754. 

Yet, how difficult it is to avoid substituting 
the sign for the thing ; how difficu!lt to keep the 
essential quality still living before us, and not to 
kill it with the word. With all this, we are ex- 
posed in modern times to a still greater danger 
by adopting expressions and terminologies from 
all branches of knowledge and science to em- 
body our views of simple nature. Astronomy, 
cosmology, geology, natural history, nay religion 
and mysticism, are called in in aid ; and how 
often do we not find a general idea and an ele- 
mentary state rather hidden and obscured than 
elucidated and brought nearer to us by the em- 
ployment of terms, the application of which is 
strictly specific and secondary. We are quite 
aware of the necessity which led to the intro- 
duction and general adoption of such a language, 
we also know that it has become in a certain 
sense indispensable ; but it is only a moderate, 
unpretending recourse to it, with an internal 
conviction of its fitness, that can recommend it. 

755. 

After all, the most desirable principle would 
be that writers should borrow the expressions . 
employed to describe the details of a given pro- 
vince of investigation from the province itself; 
treating the simplest phenomenon as an ele- 



Digitized by 



Google 



CONCLUDING OBSERVATIONS ON TERMINOLOGY. 303 

mentary formula, and deriving and developing 
the more complicated designations from this. 

756. 

The necessity and suitableness of such a con- 
ventional language where the elementary sign 
expresses the appearance itself, has been duly 



Digitized by 



Google 



304 



PART VI. 

EFFECT OF COLOUR WITH REFERENCE TO MORAL 
ASSOCIATIONS. 

758. 

Since colour occupies so important a place in 
the series of elementary phenomena, filling as it 
does the limited circle assigned to it with fullest 
variety, we shall not be surprised to find that 
its efiects are at all times decided and significant, 
and that they are immediately associated with 
the emotions of the mind. We shall not be 
surprised to find that these appearances pre- 
sented* singly, are specific, that in combination 
they may produce an harmonious, characteristic, 
often even an inharmonious efiect on the eye, 
by means of which they act on the mind ; pro- 
ducing this impression in their most general ele- 
mentary character, without relation to the nature 
or form of the object on whose surface they are 
apparent. Hence, colour considered as an ele- 
ment of art, may be made subservient to the 
highest sesthetical ends. — Note C C. 

759. 

People experience a great delight in colour, 
generally. The eye requires it as much as it 
requires light. We have only to remember the 



Digitized by 



Google 



REFERENCE TO MORAL ASSOCIATIONS. 305 

refreshing sensation we experience, if on a 
cloudy day the sun illumines a single portion of 
the scene before us and displays its colours. 
That healing powers were ascribed to coloured 
gems, may have arisen from the experience of 
this indefinable pleasure. 

760. 

The colours which we see on objects are not 
qualities entirely strange to the eye ; the organ 
is not thus merely habituated to the impres- 
sion ; no, it is always predisposed to produce 
colour of itself, and experiences a sensation of 
delight if something analogous to its own nature 
is offered to it from without ; if its susceptibility 
is distinctly determined towards a given state. 

761. 

From some of our earlier observations we can 
conclude, that general impressions produced by 
single colours cannot be changed, that they act 
specifically, and must produce definite, specific 
states in the living organ. 

762. 

They likewise produce a corresponding in- 
fluence on the mind. Experience teaches us 
that particular colours excite particular states 
of feeling. It is related of a witty Frenchman, 
'* II pr^tendoit que son ton de conversation avec 

X 



Digitized by 



Google 



306 REFERENCE TO MORAL ASSOCIATIONS. 

Madame ^toit chang6 depuis qu'elle avoit 
chaDg6 en cramoisi le meuble de son cabinet, 
qui 6toit bleu." 

763. 

In order to experience these influences com- 
pletely, the eye should be entirely surrounded 
with one colour ; we should be in a room of one 
colour, or look through a coloured glass. We 
are then identified with the hue, it attunes the 
eye and mind in mere unison with itself. 

764. 

The colours on the pltM side are yellow, red- 
yellow (orange), yellow-red (minium, cinnabar). 
The feelings they excite are quick, lively, as^ 
piring. 

YELLOW. 

765. 

This is the colour nearest the light. It ap- 
pears on the slightest mitigation of light, whe- 
ther by semi-transparent mediums or faint 
reflection from white surfaces. In prismatic 
experiments it extends itself alone and widely 
in the light space, and while the two poles re- 
main separated from each other, before it mixes 
with blue to produce green it is to be seen in its 
utmost purity and beauty. How the chemical 
yellow developes itself in and upon the white, 
has been circumstantially described in its proper 
place. 



Digitized by 



Google 



YELLOW. 307 

766. 

In its highest purity it always carries with it 
the nature of brightness, and has a serene, gay, 
softly exciting character. 

767- 



Digitized by 



Google 



308 YELLOW. 

State is agreeable and gladdening, and in its 
utmost power is serene and noble, it is, on the 
other hand) extremely liable to contamination, 
and produces a very disagreeable effect if it is 
sullied, or in some degree tends to the minus 
side. Thus, the colour of sulphur, which inclines 
to green, has a something unpleasant in it. 

771. 

When a yellow colour is communicated to dull 
and coarse surfaces^ such as common cloth, felt, 
or the like, on which it does not appear with 
full energy, the disagreeable effect alluded to is 
apparent. By a slight and scarcely perceptible 
change, the beautiful impression of fire and gold 
is transformed into one not undeserving the 
epithet foul ; and the colour of honour and joy 
reversed to that of ignominy and aversion. To 
this impression the yellow hats of bankrupts 
and the yellow circles on the mantles of Jews, 
may have owed their origin. 

RBD-YELLOW. 

772. 

As no colour can be considered as stationary, 
so we can very easily augment yellow into red- 
dish by condensing or darkening it. The colour 
increases in energy, and appears in red-yellow 
more powerful and splendid. 



Digitized by 



Google 



RED-YELLOW. 309 

773. 

All that we have said of yellow is applicable 
here. in a higher degree. The red-yellow gives 
an impression of warmth and gladness, since it 
represents the hue of the intenser glow of fire. 



Digitized by 



Google 



310 YELLOW^RED. 

pleased with this colour. Among savage nations 
the inclination for it has been universally re- 
markedy and when children^ left to themselves, 
begin to use tints, they never spare vermilion 
and minium. 

776. 

In looking steadfastly at a perfectly yellow- 
red surface, the colour seems actually to pene- 
trate the organ. It produces an extreme ex- 
citement, and still acts thus when somewhat 
darkened. A yellow-red cloth disturbs and 
enrages animals. I have known men of educa- 
tion to whom its effect was intolerable if they 
chanced to see a person dressed in a scarlet 
cloak on a grey, cloudy day. 

777. 

The colours on the minus side are blue, red- 
blue, and blue-red. They produce a restless, 
susceptible, anxious impression. 

BLUB. 

778. 

As yellow is always accompanied with light, 
so it may be said that blue still brings a prin- 
ciple of darkness with it. 

779. 
This colour has a peculiar and almost inde^ 



Digitized by 



Google 



BLUE. 311 

scribable effect on the eye. As a hue it is power- 
ful^ but it is ou the negative side, and in its 
highest purity is, a& it were, a stimulating 
negation. Its appearance, then, is a kind of 
contradiction between excitement and repose. 

780. 

. As the upper sky and distant mountains 
appear blue, so a blue surface seems to retire 
from us. 

781. 

But as we readily follow an agreeable object 
that flies from us, so we love to contemplate 
blue» not because it advances to us, but because 
it draws us after it. 

782. 

Blue gives us an impression of cold, and thus, 
again, reminds us of shade. We have before 
spoken of its affinity with black. 

783. 

Rooms which are hung with pure blue, appear 
in some degree larger, but at the same time 
empty and cold. 

784. 

The appearance of objects seen through a 
^blue glass is gloomy and melancholy. 



Digitized by 



Google 



312 BED-BLUE. 

785. 

When blue partakes in some degree of the 
pltis side, the effect is not disagreeable. Sea- 
green is rather a pleasing colour. 

BED-BLUE. 

786. 

We found yellow very soon tending to the in- 
tense state, and we observe the same progres* 
sion in blue. 

787. 

Blue deepens very mildly into red, and thus 
acquires a somewhat active character, although 
it is on the passive side. Its exciting power is, 
however, of a very different kind fix)m that of 
the red-yellow. It may be said to disturb rather 
than enliven. 

788. 

As augmentation itself is not to be arrested, 

so we feel an inclination to follow the progress 

of the colour, not^ however, as in the case of the 

red-yellow, to see it still increase in the active 

* sense, but to find a point to rest in. . 

789. 

In a very attenuated state, this colour is 
^ known to us under the name of lilac ; but even 
in this degree it has a something lively without 
gladness. 



Digitized by 



Google 



313 



BLUE-RED. 
790. 

This unquiet feeling increases as the hue pro- 
gresses, and it may be safely assumed, that a 
carpet of a perfectly pure deep blue-red would 
be intolerable. On this account, when it is used 
for dress, ribbons, or other ornaments, it is em- 
ployed in a very attenuated and light state, and 
thus displays its character as above defined, in 
a peculiarly attractive manner. 



Digitized by 



Google 



314 RED. 

origin of red, will not think it paradoxical if we 
assert that this colour partly aefu, partly po- 
tentidy includes all the other colours. 

794. 

We have remarked a constant progress or 
augmentation in yellow and blue, and seen what 
impressions were produced by the various states ; 
hence it may naturally be inferred that now, in 
the junction of the deepened extremes^ a feeling 
of satisfaction must succeed ; and thus, in phy- 
sical phenomena, this highest of all appearances 
of colour arises from the junction of two con- 
trasted extremes which have gradually prepared 
themselves for a union. 

795. 

As a pigment, on the other hand, it presents 
itself to us already formed, and is most perfect 
as a hue in cochineal ; a substance which, how- 
ever, by chemical action may be made to tend 
to the plus or the minus side, and may be con- 
sidered to have attained the central point in the 
best carmine. 

796. 

The effect of this colour is as peculiar as its 
nature. It conveys an impression of gravity 
and dignity, and at the same time of grace and 
attractiveness. The first in its dark deep state, 



Digitized by 



Google 



BSD. 3ld 

s 

the latter in its ligtit attenuated tint ; aad thus 
the dignity of age and the amiableness of youth 
may adorn itself with degrees of the same hue. 

797. 

History relates many instances of the jealousy 
of sovereigns with regard to the quality of red. 
Surrounding accompaniments of this colour 
have always a grave and magnificent effect. 

798. 

The red glass exhibits a bright landscape in 
so dreadful a hue as to inspire sentiments of awe. 



Digitized by 



Google 



316 * QBEEN. 

against, since they employ the expressions — 
^^Sot en cramoisi, m6chant en cramoisi,'' to 
mark the extreme of the silly and the repre* 
hensible. 

GREEN. 
SOL 

If yellow and blue, which we consider as the 
most fundamental and simple colours, are united 
as they first appear, in the first state of their 
action, the colour which we call green is the 
result. 

802. 

The eye experiences a distinctly grateful im- 
pression from this colour. If the two elementary 
colours are mixed in perfect equality so that 
neither predominates, the eye and the mind re-* 
pose on the result of this junction as upon a 
simple colour. The beholder has neither the 
wish nor the power to imagine a state beyond 
it. Hence for rooms to live in constantly, the 
green colour is most generally selected. 

COMPLETENESS AND HABMONY. 

803. 

We have hitherto assumed, for the sake of 
clearer explanation, that the eye can be com- 
pelled to assimilate or identify itself with a 
single colour ; but this can only be possible for 
an instant. 



Digitized by 



Google 



COMPLETENESS AND HARMONY. 317 

804. 

For when we find ourselves surrounded by a 
given colour which excites its corresponding 
sensation on the eye, and compels us by its pre- 
sence to remain in a state identical with it, this 
state is soon found to be forced, and the organ 
unwillingly remains in it. 



Digitized by 



Google 



318 COMPLETENESS AND HARMONY. 

808. 

If, again, the entire scale is presented to the 
eye externally, the impression is gladdening, 
since the result of its own operation is pre- 
sented to it in reality. We turn our attention 
therefore, in the first place, to this harmonious 
juxtaposition. 

809. 

As a very simple means of comprehending 
the principle of this, the reader has only to 
imagine a moveable diametrical index in the 
colorific circle.* The index, as it revolves round 
the whole circle, indicates at its two extremes 
the complemental colours, which, after all, may 
be reduced to three contrasts. 

810. 

Yellow demands Red-blue, 
Blue „ Red-yellow, 

Red „ Green, 

and contrariwise. 

811. 

In proportion as one end of the sup(>osed in- 
dex deviates from the central intensity of the 
colours, arranged as they are in the natural 
order, so the opposite end changes its place in 
the contrasted gradation, and by such a simple 

* Plate 1, 6g. 3. 



Digitized by 



Google 



COMPLETENESS AND HARMONY. 319 

contrivance the complemental colours may be 
indicated at any given point. A chromatic 
circle might be made for this purpose, not con* 
fined, like our own, to the leading colours, but 
exhibiting them with their transitions in an un- 
broken series. This would not be without its 
use, for w6 are here considering a very import- 
ant point which deserves all our attention.^ 

812. 

We before stated that the eye could be in 
some d^^ee pathologically affected by being 
long confined to a single colour; that^ again, 
definite moral impressions were thus produced, 
at one time lively and aspiring, at another sus- 
ceptible and anxious — now exalted to grand 
associations, now reduced to ordinary ones. We 
now observe that the demand for completeness, 
which is inherent in the organ, frees us from 
this restraint; the eye relieves itself by pro- 
ducing the opposite of the single colour forced 
upon it, and thus attains the entire impression 
which is so satisfactory to it. 

813. 

Simple, therefore, as these strictly harmo- 
nious contrasts are, as presented to us in the- 
narrow circle, the hint is important, that nature 
tends to emancipate the sense from confined 

* See Note C. 



Digitized by 



Google 



320 COlkfPLETENESS AND HARMONY. 

impressions by suggesting and producing the 
whole, and that in this instance we have a na- 
tural phenomenon immediately applicable to 
aesthetic purposes. 

814. 

While, therefore, we may assert that the chro- 
matic scale, as given by us, produces an agree- 
able impression by its ingredient hues, we may 
here remark that those have been mistaken who 
have hitherto adduced the rainbow as an exam- 
ple of the entire scale; for the chief colour, 
pure red, is deficient in it, and cannot be pro- 
duced, since in this phenomenon, as well as in 
the ordinary prismatic series, the yellow-red 
and blue-red cannot attain to a union. 

815. 

Nature perhaps exhibits no general pheno- 
menon where the scale is in complete combi- 
nation. By artificial experiments such an 
appearance may be produced in its perfect 
splendour. The mode, however, in which the 
entire series is connected in a circle, is rendered 
most intelligible by tints on paper, till after 
much experience and practice, aided by due 
susceptibility of the organ, we become penetrated 
with the idea of this harmony, and feel it present 
in our minds. 



Digitized by 



Google 



Digitized by 



Google 



322 YELLOW AND BED— BLUE AND RED. 

TELLOW AND BLUE. 
819. 

Thi3 is the simplest of such cpmbio&tions. 
It raay be said that it contains tpo little, for 
since every trace of red is wanting iq it, it is 
defective as compared with the whole scale. In 
this view it may be called poor, and as the two 
contrasting elements are in their lowest state, 
may be said to be ordinary ; yet it is recom- 
mended by its proximity to green — in short, by 
containing the ingredients of an ultimate state. 

YELLOW AND BED. 
820. 

This is a somewhat preponderating combina- 
tion, but it has a serene and magnificent effect 
The two extremes of the active side are seen 
together without conveying any idea of pro- 
gression from one to the other. As the result 
of their combination in pigments is yellow-red, 
so they in some degree represent this colour. 

BLUE AND BBP. 

821. 

The two end^ of the passive side^ with tb^ 
excess of the upper end of the active side. 
The effect of this juxtaposition approaches tha^ 
of the blue-red produced by their union. 



Digitized by 



Google 



323 

TBLLOW-&BP AND BLUE-BSD. 

822. 

These, wh^i placed together, as the deepened 
extremes of both sides, have something exciting, 
elevated : they give us a presentiment of red, 
which in physical experiments is produced by 
their nnion. 

823. 

These four combinations have also the com- 
mon quality of producing the intermediate co- 
lour of our colorific circle by their union, a 
union which actually takes place if they are 
opposed to each other in small quantities and 
seen from a distance. A surface covered with 
narrow blue and yellow stripes appears green 
at a certain distance. 

824. 

If, again, the eye sees blue and yellow next 
each other, it finds itself in a peculiar disposi- 
tion to produce green without accomplishing it, 
while it neither experiences a satisfectory sen- 
sation in contemplating the detached colours, 
nor an impression of completeness in the two. 

825. 

Thus it will be seen that it was not without 
reason we called these combinations character- 
istic ; the more so, since the character of each 

y2 



Digitized by 



Google 



324 COMBINATIONS NON-CHARACTEBISTIC. 

combination must have ia relation to that of the 
single colours of which it consists. 

COMBINATIONS NON-CHABACTERISTIC. 

826. 

We now turn our attention to the last kind of 
combinations. These are easily found in the 
circle ; they are indicated by shorter chords, for 
in this case we do not pass over an entire inter- 
mediate colour, but only the transition from one 
to the other. 

827. 

These combinations may justly be called non- 
characteristic, inasmuch as the colours are too 
nearly alike for their impression to be signifi- 
cant. Yet most of these recommend themselves 
to a certain degree, since they indicate a pro- 
gressive state, though its relations can hardly 
be appreciable. 

828. 

Thus yellow and yellow-red, yellow-red and 
red, blue and blue-red, blue-red and red^ repre- 
sent the nearest degrees of augmentation and 
culmination, and in certain relations as to quan- 
tity may produce no unpleasant effect 

829. 
The juxtaposition of yellow and green has 



Digitized by 



Google 



RELATION TO LIGHT AND DARK. 325 

always something ordinary, but in a cheerful 
sense ; blue and green, on the other hand, is 
ordinary in a repulsive sense. Our good fore- 
fathers called these last fool's colours. 

RELATION OF THE COMBINATIONS TO LIGHT 
AND DARK. 



Digitized by 



Google 



326 CONSIDEaATIONB DEBITED FBOH THE 

be varied to infinity, still all that is api^icable 
with regard to the pure colours will be appli- 
cable in these cases. 

CONSIDERATIONS DERIVED FROM THE EVIDENCE 
OF EXPERIENCE AND HISTORY. 

833. 

The principles of the harmony of colours 
having been thus far defined, it may not be 
irrelevant to review what has been adduced in 
connexion with experience and historical ex- 
amples. 

834. 
The principles in question have been derived 
from the constitution of our nature and the 
constant relations which are found to obtain in 
chromatic phenomena. In experience we find 
much that is in conformity with these principles, 
and much that is opposed to them. 

836. 
Men in a state of nature, uncivilised nations, 
children, have a great fondness for colours in 
their utmost brightness, and especially for yel- 
low-red : they are also pleased with the motley. 
By this expnession we understand the juxtapo- 
sition of vivid coKmrs without an harmonious 
balance; but if this balance is observed, through 
instinct or accident, an agreeable effect may be 
produced. I remember a Hes^n officer, re- 



Digitized by 



Google 



EYIDENCS or EXPERltNCE AND HISTORY. 327 

turned tram Americd, who had paunted his face 
with the positive colours, in the manner of the 
Indians ; a kind of completeness or due balance 
was thus produced, the effect of which was not 
disagreeafaie. 

836. 
The inhabitants of the south of Europe make 
use of very brilliant colours for their dresses. 
The circumstance of their procuring silk stuffs 
at a cheap rate is favourable to this propen- 
sity. The women, especially, with their bright- 
coloured bodices and ribbons, are always in 
harmony with the scenery, since they cannot 
possibly surpass the splendour of the sky and 
landscape. 

837. 
The history of dyeing teaches us that certain 
technical conveniences and advantages have had 
great influence on the costume of nations. We 
find that the Germans wear blue very generally 
because it is a permanent colour in cloth ; so in 
many districts all the country people wear green 
twill, because that material takes a green dye 
well. If a traveller were to pay attention to 
these circumstances, he might collect some 
amusing and curious facts. 

838. 
Colours, as connected with particular frames 



Digitized by- 



Google 



328 CONSIDERATIONS DEBITED FROM THE 

of mind, are again a consequence of peculiar 
character and circumstances. Lively nations, 
the French for instance, love intense colours, 
especially on the active side; sedate nations, 
like the English and Germans, wear straw- 
coloured or leather-coloured yellow accom- 
panied with dark blue. Nations aiming at 
dignity of appearance, the Spaniards and Ita- 
lians for instance, suffer the red colour of their 
mantles to incline to the passive side. 

839. 

In dress we associate the character of the 
colour with the character of the person. We 
may thus observe the relation of colours singly, 
and in combination, to the colour of the com- 
plexion, age, and station. 

840. 

The female sex in youth is attached to rose- 
colour and sea-green, in age to violet and dark- 
green. The fair-haired prefer violet, as opposed 
to light yellow, the brunettes, blue, as opposed 
to yellow-red, and all on good grounds. The 
Roman emperors were extremely jealous with 
regard to their purple. The robe of the Chinese 
Emperor is orange embroidered with red ; his 
attendants and the ministers of religion wear 
citron-yellow. 



Digitized by 



Google 



EVIDENCE OF EXPERIENCE AND HISTORY. 329 
841. 

People of refinement have a disinclination to 
colours. This may be owing partly to weakness 
of sight, partly to the uncertainty of taste, 
which readily takes refuge in absolute negation. 
Women now appear almost universally in white 
and men in black. 

842. 



843. 

Black was intended to remind the Venetian 
noblemen of republican equality. 



Digitized by 



Google 



330 .fiSTHBTlC INFLUENCE. 

846. 

It 1$ also to be remarked that ladies, in wear- 
ing positive colours, are in danger of making a 
complexion which may not be rery bright still 
lesfl! so> and thus to preserve a dne balance with 
such brillidfit accompaniments, they are induced 
to heighten their complexions artificially. 

847. 

An amusing inquiry might be made which 
would lead to a critique of uniforms, liveries, 
cockades, and other distinctions, according to 
the principles above hinted at. It might be 
observed, generally, that such dresses and in- 
signia should not be composed of harmonious 
colours. Uniforms should be characteristic and 
dignified ; liveries might t>e ordinary and strik- 
ing to the eye. Examples both good and bad 
would not be wanting, since the scale of colours 
usually employed for such purposes is limited, 
and its varieties have been often enotigii tried.* 

JBSTHETIC INFLUENCE. 

848. 

From the moral associations connected with 
the appearance of colours, single or coniibined, 
their sesthetic influence mfay Aow he deduced 

♦ Some early Italian writere, Sicillo, Occolti, Rinaldi, and 
others, dave treated this subject in connexion with the supposed 
signification of colours. — ^T. 



Digitized by 



Google 



CHIARO-SCUBO. 331 

for the artist. We shall touch the most essential 
points to be attended to after first considering 
the general condition of pictorial representa- 
tion, light and shade, with which the appearance 
of colaar is itnmedidtel j connected. 



Digitized by 



Google 



332 CHIABO-SCUBO. 

853. 
We have here to consider the highest light, 
the middle tint, and the shadow, and in the last 
the shadow of the object itself, the shadow it 
casts on other objects, and the illumined shadow 
or reflexion. 

854. 
The globe is well adapted for the general ex- 
emplification of the nature of chiaro-scuro, but 
it is not altogether sufficient. The softened 
unity of such complete rotundity tends to the 
vapoury, and in order to serve as a principle for 
efiects of art, it should be composed of plane 
surfaces, so as to define the gradations more. 

855. 
The Italians call this manner '* il piazzoso ;" 
in German it might be called " das Flachen- 
hafte."* If, therefore, the sphere is a perfect 
example of natural chiaro-scuro, a polygon 
would exhibit the artist-like treatment in which 
all kinds of lights, half-lights, shadows, and 
reflexions, would be appreciable. — Note E E. 

856. 
The bunch of grapes is recognised as a good 
example of a picturesque completeness in chiaro- 
scuro, the more so as it is fitted, from its form, 
to represent a principal group ; but it is only 

* The English technical expressions **flat'* and "square** 
have an association of mannerism. — ^T. 



Digitized by 



Google 



CHIARO-SCURO. 333 

available for the master who can see in it what 
he has the power of producing. 

857. 

In order to make the first idea intelligible to 
the beginner, (for it is difficult to consider it 
abstractedly even in a polygon,) we may take 
a cube, the three sides of which that are seen 
represent the light, the middle tint, and the 
shadow in distinct order. 

858. 

To proceed again to the chiaro-scuro of a 
more complicated figure, we might select the 
example of an open book, which presents a 
greater diversity. 



Digitized by 



Google 



334 TENDENCY TO COLOUR. 

861. 

Modern examples may be found in single 
figures by Raphael, in entire works by Cor- 
reggio, and also by the Flemish masters, espe- 
cially Rubens. 

TENDENCY TO COLOUR. 

862. 

A picture in black and white seldom makes 
its appearance; some works of Polidoro are 
examples of this kind of art. Such works, in- 
asmuch as they can attain form and keeping, 
are estimable, but they have little attraction 
for the eye, since their very existence supposes 
a violent abstraction. 

863. 

If the artist abandons himself to his feeling, 
colour presently announces itself. Blade no 
sooner inclines to blue than the eye demands 
yellow, which the artist instinctively modifies, 
and introduces partly pure in the light, partly 
reddened and subdued as brown, in the reflexes, 
thus enlivening the whole. — Note G G. 

864. 

All kinds of camayeu, or colour on similar 
colour, end in the introduction either of a com- 
plemental contrast, or some variety of hue. 
Thus, Polidoro in his black and white frescoes 



Digitized by 



Google 



TENDENCY TO COLOUR. «1i35 

sometimes introduced a yellow vase, or some- 
thing of the kind. 

865. 

In general it may be observed that men have 
at all times instinctively striven after colour in 
the practice of the art. We need only observe 
daily, how soon amateurs proceed from colour- 
less to coloured materials. Paolo Uccello 
paintedcoloured landscapes to colourless figures. 
—Note H H. 



Digitized by 



Google 



336 KEEPING. 

tion in greater or less distinctness, as affected 
by the same cause. 

868. 
Although from the nature of the organ of 
sight, we cannot see distant objects so distinctly 
as nearer ones, yet aerial perspective is grounded 
strictly on the important fact that all mediums 
called transparent are in some degree dim. 

869. 

The atmosphere is thus always, more or less, 
semi-transparent. This quality is remarkable 
in southern climates, even when the barometer 
is high, the weather dry, and the sky cloudless, 
for a very pronounced gradation is observable 
between objects but little removed from each 
other. 

870. 

The appearance on a large scale is known to 
every one; the painter, however, sees or be- 
lieves he sees, the gradation in the slightest 
varieties of distance. He exemplifies it practi- 
cally by making a distinction, for instance, in 
the features of a face according to their relative 
position as regards the plane of the picture. 
The direction of the light is attended to in like 
manner. This is considered to produce a gra- 
dation from side to side, while keeping has re- 
ference to depth, to the comparative distinctness 
of near and distant things. 



Digitized by 



Google 



337 



COLOURING. 



871. 

In proceeding to consider this subject, we 
assume that the painter is generally acquainted 
with our sketch of the theory of colours, and 
that he has made himself well acquainted with 
certain chapters and rubrics which especially 
concern him. He will thus be enabled to make 
use of theory as well as practice in recognising 
the principles of effect in nature, and in em- 
ploying the means of art. 

COLOUR IN GENERAL NATURE. 

872. 

The first indication of colour announces itself 
in nature together with the gradations of aerial 
perspective ; for aerial perspective is intimately 
connected with the doctrine of semi-transparent 
mediums. We see the sky, distant objects and 
even comparatively near shadows, blue. At the 
same moment, the illuminating and illuminated 
objects appear yellow, gradually deepening to 
red. In many cases the physiological sugges- 
tion of contrasts comes into the account, and 
an entirely colourless landscape, by means of 
these assisting and counteracting tendencies, 
appears to our eyes completely coloured. 



Digitized by 



Google 



338 

COLOUR OF PARTICULAR OBJECTS. 

873. 

Local colours are composed of the general 
elementary colours; but these are determined 
or specified according to the properties of sub- 
stances and surfaces on which they appear: 
this specification is infinite. 

874. 

Thus, there is at once a great difference be- 
tween silk and wool similarly dyed. Every 
kind of preparation and texture produces corre- 
sponding modifications. Roughness, smooth- 
ness, polish, all are to be considered. 

875. 

It is therefore one of the pernicious prejudices 
of art that the skilful painter must never attend 
to the material of draperies, but always repre- 
sent, as it were, only abstract folds. Is not all 
characteristic variety thus done away with, and 
is the portrait of Leo X. less excellent because 
velvet, satin, and moreen, are imitated in their 
relative effect ? 

876. 

In the productions of nature, colours appear 
more or less modified, specified, even indivi- 
dualised : this may be readily observed in mine- 



Digitized by 



Google 



COLOUR OF PARTICULAR OBJECTS. 339 

rals and plants, in the feathers of birds and the 
skins of beasts. 

877, ' 

The chief art of the painter is always to imi- 
tate the actual appearance of the definite hue, 
doing away with the recollection of the ele- 
mentary ingredients of colour. This difficulty 
is in no instance greater than in the imitation 
of the surface of the human figure. 

878. 

The colour of flesh, as a whole, belongs to the 
active side, yet the bluish of the passive side 
mingles with it. The colour is altogether re- 
moved from the elementary state and neutralised 
by organisation. 

879. 

To bring the colouring of general nature into 
harmony with the colouring of a given object, 
will perhaps be more attainable for the judicious 
artist after the consideration of what has been 
pointed out in the foregoing theory. For the 
most fancifully beautiful and varied appear- 
ances may still be made true to the principles 
of nature. 

CHARACTERISTIC COLOURING. 

880. 

The combination of coloured objects, as well 
as the colour of their ground, should depend on 

z2 



Digitized by 



Google 



340 CHARACTERISTIC COLOURING. 

considerations which the artist pre-establishes 
for himself. Here a reference to the effect of 
colours singly or combined, on the feelings, is 
especially necessary. On this account the 
painter should possess himself with the idea of 
the general dualism, as well as of particular 
contrasts^ not forgetting what has been adverted 
to with regard to the qualities of colDurs. 

881. 
The characteristic in colour may be compre- 
hended under three leading rubrics, which we 
here define as the powerful, the soft, and the 
splendid. 

882. 

The first is produced by the preponderance of 
the active side, the second by that of the passive 
side, and the third by completeness, by the ex- 
hibition of the whole chromatic scale in due 
balance. 

883. 

The powerful impression is attained by yellow, 
yellow-red, and red, which last colour is to be 
arrested on the plus side. But little violet and 
blue, still less green, are admissible. The soft 
effect is produced by blue, violet, and red, which 
in this case is arrested on the minus side ; a 
moderate addition of yellow and yellow-red, but 
much green may be admitted. 



Digitized by 



Google 



HARMONIOUS COLOURING. 341 

884. 

If it is proposed to produce both these effects 
in their full significancy, the complemental 
colours may be excluded to a minimum, and 
only so much of them may be suffered to appear 
as is indispensable to convey an impression of 
completeness. 

HARMONIOUS COLOURING. 

885. 

Although the two characteristic divisions as 
above defined may in some sense be also called 
harmonious, the harmonious effect, properly so 
called^ only takes place when all the colours are 
exhibited together in due balance. 

886. 

In this way the splendid as well as the agree- 
able may be produced ; both of these, however, 
have of necessity a certain generalised effect, 
and in this sense may be considered the reverse 
of the characteristic. 

887. 

This is the reason why the colouring of most 
^ modern painters is without character, for, while 
they follow their general instinctive feeling only, 
the last result of such a tendency must be mere 
completeness; this, they more or less attain, 
but thus at the same time neglect the charac- 



Digitized by 



Google 



342 HARMONIOUS COLOURING. 

teristic impression which the subject might 
demand. 

888. 

But if the principles before alluded to are 
kept in view, it must be apparent that a distinct 
style of colour may be adopted on safe grounds 
for every subject. The application requires, it 
is true, infinite modifications, which can only 
succeed in the hands of genius. 

GENUINE TONE. 

889. 

If the word tone, or rather tune, is to be still 
borrowed in future from music, and applied to 
colouring, it might be used in a better sense 
than heretofore. 

890. 

For it would not be unreasonable to compare 
a painting of powerful effect, with a piece of 
music in a sharp key ; a painting of soft effect 
with a piece of music in a fiat key, while, other 
equivalents might be found for the modifications 
of these two leading modes. 

FALSE TONE. 
891. 

The word tone has been hitherto understood 
to mean a veil of a particular colour spread over 



Digitized by 



Google 



FALSE TONE. 343 

the whole picture ; it was generally yellow, for 
the painter instinctively pushed the eflTect to- 
wards the powerful side. 

892. 

If we look at a picture through a yellow glass 
it will appear in this tone. It is worth while to 
make this experiment again and again, in order 
to observe what takes place in such an opera- 
tion. It is a sort of artificial light, deepening, 
and at the same time darkening the pltcs side, 
and neutralising the minus side. 

893. 

This spurious tone is produced instinctively 
through uncertainty as to the means of attain- 
ing a genuine effect ; so that instead of com- 
pleteness, monotony is the result. 

WEAK COLOURING. 
894. 

It is owing to the same uncertainty that the 
colours are sometimes so much broken as to 
have the effect of a grey camayeu, the handling 
being at the same time as delicate as possible. 

895. 

The harmonious contrasts are often found to 
be very happily felt in such pictures, but with- 
out spirit, owing to a dread of the motley. 



Digitized by 



Google 



344 

THB MOTLEY. 

896. 

A picture may easily become party-coloured 
or motley, when the colours are placed next each 
other in their full force, as it were only mechani- 
cally and according to uncertain impressions. 

897. 

If, on the other hand, weak colours are com- 
bined, even although they may be dissonant, 
the effect, as a matter of course, is not striking. 
The uncertainty of the artist is communicated 
to the spectator, who, on his side, can neither 
praise nor censure. 

898. 

It is also important to observe that the colours 
may be disposed rightly in themselves, but that 
a work may still appear motley, if they are 
falsely arranged in relation to light and shade. 

899. 

This may the more easily occur as light and 
shade are already defined in the drawing, and 
are, as it were, comprehended in it, while the 
colour still remains open to selection. 

DREAD OF THEORY. 
900. 

A dread of, nay, a decided aversion for all 



Digitized by 



Google 



ULTIMATE AIM— GROUNDS. 345 

theoretical views respecting colour and every- 
thing belonging to it, has been hitherto found to 
exist among painters; a prejudice for which, 
after all, they were not to be blamed ; for what 
has been hitherto called theory was groundless, 
vacillating, and akin to empiricism. We hope 
that our labours may tend to diminish this pre- 
judice, and stimulate the artist practically to 
prove and embody the principles that have been 
explained. 

ULTIMATE AIM. 
. 901. 

But without a comprehensive view of the 
whole of our theory, the ultimate object will not 
be attained. Let the artist penetrate himself 
with all that we have stated. It is only by 
means of harmonious relations in light and 
shade, in keeping, in true and characteristic 
colouring, that a picture can be considered com- 
plete, in the sense we have now learnt to attach 
to the term. 

GROUNDS. 

902. 

It was the practice of the earlier artists to 
paint on light grounds. This ground consisted 
of gypsum, and was thickly spread on linen or 
panel, and then levigated. After the outline 
was drawn, the subject was washed in with a 



Digitized by 



Google 



346 GROUNDS. 

blackish or brownish colour. Pictures prepared 
in this manner for colouring are still in exist- 
ence, by Leonardo da Vinci, and Fra Bar- 
tolomeo; there are also several by Guido. — 
Note 1 1. 

903. 

When the artist proceeded to colour, and had 
to represent white draperies, he sometimes suf- 
fered the ground to remain untouched. Titian 
did this latterly when he had attained the 
greatest certainty in practice, and could accom- 
plish much with little labour. The whitish 
ground was left as a middle tint, the shadows 
painted in, and the high lights touched on. — 
Note K K. 

904. 

In the process of colouring, the preparation 
merely washed as it were underneath, was 
always effective. A drapery, for example, was 
painted with a transparent colour, the white 
ground shone through it and gave the colour 
life, so the parts previously prepared for sha- 
dows exhibited the colour subdued, without 
being mixed or sullied. 

905. 

This method had many advantages ; for the 
painter had a light ground for the light portions 
of his work and a dark ground for the shadowed 
portions. The whole picture was prepared ; the 



Digitized by 



Google 



GROUNDS. 347 

artist could work with thin colours in the sha- 
dows, and had always an internal light to give 
value to his tints. In our own time painting in 
water colours depends on the same principles. 

906. 

Indeed a light ground is now generally em- 
ployed in oil-painting, because middle tints 
are thus found to be more transparent, and are 
in some degree enlivened by a bright ground ; 
the shadows, again, do not so easily become 
black. 

907. 

It was the practice for a time to paint on 
dark grounds. Tintoret probably introduced 
them. Titian's best pictures are not painted on 
a dark ground. 

908. 

The ground in question was red-brown, and 
when the subject was drawn upon it, the 
strongest shadows were laid in ; the colours of 
the lights impasted very thickly in the bright 
parts, and scumbled towards the shadows, so 
that the dark ground appeared through the thin 
colour as a middle tint Effect was attained in 
finishing by frequently going over the bright 
parts and touching on the high lights. 



Digitized by 



Google 



348 GROUNDS. 

909. 

If this method especially recommended itself 
in practice on account of the rapidity it allowed 
of, yet it had pernicious consequences. The 
strong ground increased and became darker, 
and the light colours losing their brightness by 
degrees, gave the shadowed portions more and 
more preponderance. The middle tints became 
darker and darker, and the shadows at last quite 
obscure. The strongly impasted lights alone 
remained bright, and we now see only light 
spots on the painting. The pictures of the 
Bolognese school, and of Caravaggio, afford 
sufficient examples of these results. 

910. 

We may here in conclusion observe, that 
glazing derives its effect from treating the pre- 
pared colour underneath as a light ground. By 
this operation colours may have the effect of 
being mixed to the eye, may be enhanced, and 
may acquire what is called tone ; but they thus 
necessarily become darker. 

PIGMENTS. 

911. 

We receive these from the hands of the che- 
mist and the investigator of nature. Much has 
been recorded respecting colouring substances, 



Digitized by 



Google 



PIGMENTS. 349 

which is familiar to all by means of the press. 
But such directions require to be revised from 
time to time. The master meanwhile communi- 
cates his experience in these matters to his 
scholar, and artists generally to each other. 

912. 

Those pigments which according to their 
nature are the most permanent, are naturally 
much sought after, but the mode of employing 
them also contributes much to the duration of a 
picture. The fewest possible colouring mate- 
rials are to be employed, and the simplest me- 
thods of using them cannot be sufficiently re- 
commended. 

913. 

For from the multitude of pigments colour- 
ing has suffered much. Every pigment has its 
peculiar nature as regards its effect on the eye ; 
besides this it has its peculiar quality, requiring 
a corresponding technical method in its appli- 
cation. The former circumstance is a reason 
why harmony is more difficult of attainment 
with many materials than with few, the latter, 
why chemical action and re-action may take 
place among the colouring substances. 

914. 
We may refer, besides, to some false ten- 



Digitized by 



Google 



350 PIGMENTS. 

dencies which the artists suffer themselves to 
be led away with. Painters are always looking 
for new colouring substances, and believe when 
such a substance is discovered that they have 
made an advance in the art. They have a great 
curiosity to know the practical methods of the 
old masters, and lose much time in the search. 
Towards the end of the last century we were 
thus long tormented with wax-painting. Others 
turn their attention to the discovery of new 
methods, through which nothing new is accom- 
plished ; for, after all, it is the feeling of the 
artist only that informs every kind of technical 
process. 

ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION 
OF COLOUR. 

915. 

It has been circumstantially shown above, 
that every colour produces a distinct impression 
on the mind, and thus addresses at once the eye 
and feelings. Hence it follows that colour may 
be employed for certain moral and aesthetic ends. 

916. 

Such an application, coinciding entirely with 
nature, might be called symbolical, since the 
colour would be employed in conformity with 
its effect, and would at once express its mean- 
ing. Iff for example, pure red were assumed to 



Digitized by 



Google 



AXLEGORICAL APPLICATION OF COLOUR. 351 

designate majesty, there can be no doubt that 
this would be admitted to be a just and expres- 
sive symbol. All this has been already suffi- 
ciently entered into. 

917. 

Another application is nearly allied to this ; 
it might be called the allegorical applica- 
tion. In this there is more of accident and 
caprice, inasmuch as the meaning of the sign 
must be first communicated to us before we 
know what it is to signify ; what idea, for in- 
stance, is attached to the green colour, which 
has been appropriated to hope ? 

918. 

That, lastly, colour may have a mystical al- 
lusion, may be readily surmised, for since every 
diagram in which the variety of colours may be 
represented points to those primordial relations 
which belong both to nature and the organ of 
vision, there can be no doubt that these may be 
made use of as a language, in cases where it is 
proposed to express similar primordial relations 
which do not present themselves to the senses 
in so powerful and varied a manner. The ma- 
thematician extols the value and applicability 
of the triangle ; the triangle is revered by the 
mystic ; much admits of being expressed in it 
by diagrams, and, among other things, the law 



Digitized by 



Google 



352 ALLEGORICAL APPLICATION OF COLOUR, 

of the phenomena of colours ; in this case, in- 
deed, we presently arrive at the ancient myste- 
rious hexagon. 

919. 

When the distinction of yellow and blue is 
duly comprehended, and especially the augmen- 
tation into red, by means of which the opposite 
qualities tend towards each other and become 
united in a third ; then, certainly, an especially 
mysterious interpretation will suggest itself, 
since a spiritual meaning may be connected 
with these facts ; and when we find the two se- 
parate principles producing green on the one 
hand and red in their intenser state, we can 
hardly refrain from thinking in the first case on 
the earthly, in the last on the heavenly, genera- 
tion of the Elohim. — Note L L. 

920. 

But we shall do better not to expose our- 
selves, in conclusion, to the suspicion of enthu- 
siasm; since, if our doctrine of colours finds 
favour, applications and allusions, allegorical, 
symbolical, and mystical, will not fail to be 
made, in conformity with the spirit of the age. 

CONCLUDING OBSERVATIONS. 

In reviewing this labour, which has occupied 
me long, and which at last I give but as a 



Digitized by 



Google 



CONCLUDING OBSERVATIONS. 353 

sketch, I am reminded of a wish once expressed 
by a careful writer, who observed that he would 
gladly see his works printed at once as he con- 
ceived them, in order then to go to the task with 
a fresh eye ; since everything defective presents 
itself to us more obviously in print than even in 
the cleanest manuscript. This feeling may be 
imagined to be stronger in my case, since I had 
not even an opportunity of going through a fair 
transcript of my work before its publication, 
these pages having been put together at a time 
when a quiet, collected state of mind was out of 
the question.* 

Some of the explanations I was desirous of 
giving are to be found in the introduction, but 
in the portion of my work to be devoted to the 
history of the doctrine of colours, I hope to give 
a more detailed account of my investigations 
and the vicissitudes they underwent. One in- 
quiry, however, may not be out of place here ; 
the consideration, namely, of the question, what 
can a man accomplish who cannot devote his 
whole life to scientific pursuits? what can he 
perform as a temporary guest on an estate not 
his own, for the advantage of the proprietor? 

When we consider art in its higher character, 
we might wish that masters only had to do with 

* Towards the close of 1806, wheu Weimar was occupied by 
Napoleon after the battle of Jena. — ^T. 

2 A 



Digitized by 



Google 



354 CONCLUDING OBSERVATIONS. 

it, that scholars should be trained by the se- 
verest study, that amateurs might feel them- 
selves happy in reverentially approaching its 
precincts. For a work of art should be the 
effusion of genius, the artist should evoke its 
substance and form from his inmost being, treat 
his materials with sovereign command, and 
make use of external influences only to accom- 
plish his powers. 

But if the professor in this case has many 
reasons for respecting the dilettante, the man of 
science has every motive to be still more indul- 
gent, since the amateur here is capable of con- 
tributing what may be satisfactory and useful. 
The sciences depend much more on experiment 
than art, and for mere experiment many a vo- 
tary is qualified. Scientific results are arrived 
at by many means, and cannot dispense with 
many hands, many heads. Science may be 
communicated, the treasure may be inherited, 
and what is acquired by one may be appropri- 
ated by many. Hence no one perhaps ought 
to be reluctant to offer his contributions. How 
much da we not owe to accident, to mere prac- 
tice, to momentary observation. All who are 
endowed only with habits of attention, women, 
children, are capable of communicating striking 
and true remarks. 

In science it cannot therefore be required, 
that he who endeavours to furnish something in 



Digitized by 



Google 



CONCLUDING OBSERVATIONS. 355 

its aid should devote his whole life to it, should 
survey and investigate it in all its extent ; for 
this, in most cases, would be a severe condition 
even for the initiated. But if we look through 
the history of science in general, especially the 
history of physics, we shall find that many im- 
portant acquisitions have been made by single 
inquirers, in single departments, and very often 
by unprofessional observers. 

To whatever direction a man may be deter- 
mined by inclination or accident, whatever 
class of phenomena especially strike him, excite 
his interest, fix his attention, and occupy him, 
the result will still be for the advantage of 
science: for every new relation that comes to 
light, every new mode of investigation, even the 
imperfect attempt, even error itself is available; 
it may stimulate other observers and is never 
without its use as influencing future inquiry. 

With this feeling the author himself may look 
back without regret on his endeavours. From 
this consideration he can derive some encou- 
ragement for the prosecution of the remainder 
of his task ; and although not satisfied with the 
result of his efibrts, yet re-assured by the sin- 
cerity of his intentions, he ventures to recom- 
mend his past and future labours to the interest 
of his contemporaries and posterity. 

Multi pertransibant et augebitur Bcientia. 

2 a2 



Digitized by 



Google 



Digitized by 



Google 



NOTES. 



NOTE A.— Par. 18. 

Leonardo da Vinci observes that ''a light object relieved 
on a dark ground appears magnified ;'' and again^ '^ Objects 
seen at a distance appear out of proportion ; this is because 
the light parts transmit their rajs to the eye more powerfully 
than the dark. A woman*s white head-dress once appeared 
to me much wider than her shoulders, owing to their being 
dressed in black.*'* ^' It is now generally admitted that the 
excitation produced by light is propagated on the retina a 
little beyond the outline of the image. Professor Plateau, 
of Ghent, has devoted a very interesting special memoir to 
the description and explanation of phenomena of this nature. 
See his ^ Memoire sur Tlrradiation,' published in the 11th 
vol. of the Transactions of the Royal Academy of Sciences 
at Brussel8."t— S. F. 

NOTE B.— Par. 23. 

" The duration 6f ocular spectra produced by strongly 
exciting the retina, may be conveniently measured by 
minutes and seconds ; but to ascertain the duration of more 
evanescent phenomena, recourse must be had to other 
means. The Chevalier d*Arcy (Mem. de TAcad. des Sc. 



^ *< Trattato della Pittura, Roma, 1817,'' p. 143—223. This edltioD, pub- 
lished from a Vatican MS., contains many observations not included in 
former editions. 

t A few notes (marked with inverted commas and with the signature S. F.) 
bare been kindly furnished by a scientific friend. 



Digitized by 



Google 



358 NOTES. 

1760^) endeavoured to ascertain the duration of the impres- 
sion produced by a glowing coal in the following manner. 
He attached it to the circumference of a wheels the velocity 
of which was gradually increased until the apparent trace of 
the object formed a complete circle, and then measured the 
duration of a revolution, which was obviously that of the 
impression. To ascertain the duration of a revolution it is 
sufficient merely to know the number of revolutions described 
in a given time. Recently more refined experiments of the 
same kind have been made by Professors Plateau and 
Wheatstone."— S. F. 

NOTE C— Par. 50. 

Every treatise on the harmonious combination of colours 
contains the diagram of the chromatic circle more or less 
elaborately constructed. These diagrams, if intended to 
exhibit the contrasts produced by the action and re-action of 
the retina, have one common defect. The opposite colours 
are made equal in intensity ; whereas the complemental 
colour pictured on the retina is always less vivid, and always 
darker or lighter than the original colour. This variety un- 
doubtedly accords more with harmonious effects in painting. 

Thfe opposition of two pure hues of equal intensity, dif- 
fering only in the abstract quality of colour^ would imme- 
diately be pronounced crude and inharmonious. It would 
not, however, be strictly correct to say that such a contrast 
is too violent ; on the contrary, it appears the contrast is not 
carried far enough, for though differing in colour, the two 
hues may be exactly similar in purity and intensity. Com- 
plete contrast, on the other hand, supposes dissimilarity in 
all respects. 

In addition to the mere difference of hue, the eye, it 
seems, requires difference in the lightnesi^ or darkness of the 
hue. The spectrum of a colour relieved as a dark on a 
light ground, is a light colour on a dark ground, and vice 
versa. Thus, if we look at a bright red wafer on the whitest 



Digitized by 



Google 



NOTES. 359 

surface^ the complemental image will be still lighter than 
the white surface ; if the same wafer is placed on a black 
surface^ the complemental image will be still darker. The 
colour of both these spectra may be called greenish, but it 
is evident that a colour must be scarcely appreciable as such, 
if it is lighter than white and darker than black. It is, 
however, to be remarked, that the white surface round the 
light greenish image seems tinged with a reddish hue, and 
the black surface round the dark image becomes slightly 
illuminated with the same colour, thus in both cases assist- 
ing to render the image apparent (58). 

The di£5culty or impossibility of describing degrees of 
colour in words, has also had a tendency to mislead, by con- 
veying the idea of more positive hues than the physiological 
contrast warrants. Thus, supposing scarlet to be relieved 
as a dark, the complemental colour is so light in degree and 
so faint in colour, that it should be called a pearly grey ; 
whereas the theorists^ looking at the quality of colour ab- 
stractedly, would call it a green- blue, and the diagram 
would falsely present such a hue equal in intensity to scarlet, 
or as nearly equal as possible. 

Even the difference of mass which good taste requires 
may be suggested by the physiolc^cal phenomena, for unless 
the complemental image is suffered to fall on a surface pre- 
cisely as near to the eye as that on which the original colour 
was displayed, it ap|^eard larger or smaller than the original 
object (22), and this in a rapidly increasing proportion. 
Lastly, the shape itself soon becomes changed (26). 

That vivid colour demands the comparative absence of 
colour, either on a lighter or darker scale, as its contrast, 
may be inferred again from the fact that bright colourless 
objects produce strongly coloured spectra. In darkness, 
the spectrum which is first white, or nearly white, is fol- 
lowed by red : in light, the spectrum which is first black, is 
followed by green (39—44). All colour, as the author ob- 
serves (259)» is to be considered as half-light, inasmuch as it 



Digitized by 



Google 



J 



360 NOTES. 

is in every case lighter than black and darker tUan white. 
Hence no contrast of colour with colour^ or even of colour 
with black or white^ can be so great (as regards lightness or 
darkness) as the contrast of black and white^ or light and 
dark abstractedly. This distinction between the differences 
of degree and the differences of kind is important, since a 
just application of contrast in colour may be counteracted 
by an undue difference in lightness or darkness. The mere 
contrast of colour is happily employed in some of Guido*s 
lighter pictures, but if intense darks had been opposed to his 
delicate carnations, their comparative whiteness would have 
been unpleasantly apparent. On the other hand, the flesh- 
colour in Giorgione, Sebastian del Piombo (his best imi- 
tator), and Titian, was sometimes so extremely glowing* that 
the deepest colours, and black, were indispensable accom- 
paniments. The manner of Titian as distinguished from 
his imitation of Giorgione, is golden rather than fiery, and 
his biographers are quite correct in saying that he was fond 
of opposing red (lake) and blue to his flesh, f The cor- 
respondence of these contrasts with the physiological phe- 
nomena will be immediately apparent, while the occasional 
practice of Rubens in opposing bright red to a still cooler 
flesh-colour, will be seen to be equally consistent. 

The effect of white drapery (the comparative absence of 
colour) in enhancing the glow of Titian*s flesh-colour, has 
been frequently pointed out:^ the shadows of white thus 
opposed to flesh, often present, again, the physiological con- 
trast, however delicately, according to the hue of the cama- 

^ " Ardito veramente alquanto, sanguigno, e quasi 0ainmeggiante%" 
— Zanetti delta Pittura Ftntxicma^ Ven. 1771, p. 90. Warm as the flesh 
colour of the colourists is, it still never approaches a positive hue, if we except 
some examples in frescoes and other works intended to be seen at a great 
distance. Zanotti, speaking of a fresco by Giorgione, now almost obliterated, 
compares the colour to '* un vivo raggio di cocente sole."— 'f^ortf PUturt a 
fretco dei Principali Maestri FenezianL Ven. 1760. 

t Ridolfi. 

\ Zanetti, I. it. 



Digitized by 



Google 



NOTES. 361 

tion. The lights, on the other hand> are not, and probably 
never were^ quite white^ but from the firsts partook of the 
quality of depth, a quality assumed by the colourists to per- 
vade every part of a picture more or less.* 

It was before observed that the description of colours in 
words may often convey ideas of too positive a nature, and it 
may be remarked generally that the colours employed by 
the great masters are, in their ultimate effect, more or less 
subdued or broken. The physiological contrasts are, how- 
ever, still applicable in the most comparatively neutral 
scale. 

Again, the works of the colourists show that these oppo* 
sitions are not confined to large masses (except perhaps in 
works to be seen only at a great distance) ; on the contrary, 
they are more or less apparent in every part, and when at 
last the direct and intentional operations of the artist may 
have been insufficient to produce them in their minuter 
d^rees, the accidental results of glazing and other methods 
may be said to extend the contrasts to infinity. In such 
productions, where every smallest portion is an epitome of 
the whole, the eye still appreciates the fascinating effect of 
contrast, and the work is pronounced to be true and com- 
plete, in the best sense of the words. 

The Venetian method of scumbling and glazing exhibits 
these minuter contrasts within each other, and is thus gene- 
rally considered more refined than the system of breaking 
the colours, since it ensures a fuller gradation of hues, and 
produces another class of contrasts, those, namely, which re- 
sult from degrees of transparence and opacity. In some of 
the Flemish and Dutch masters, and sometimes in Reynolds, 
the two methods are combined in great perfection. 

^ Two great authorities, divided by more than three centuries, Leon Bat- 
tista Alberti and Re3rno1d8, hare recommended this subdued treatment of 
white. " It is to be remembered," says the first, " that no surface should be 
made so white that it cannot be made more so. In white dresses again, it 
is necessary to stop far short of the last degree of whiteness." — Delia Pittwroy 
1, ii., compare with Reynolds, vol. i. dis. 8. 



Digitized by 



Google 



362 NOTES. 

The chromatic diagram does not appear to be older than 
the last century. It is one of those happy ads^tations of 
exacter principles to the objects of taste which might hare 
been expected from Leonardo da Vinci. That its true 
principle was duly felt is abundantly evident from the works 
of the colourists> as well as from the general observations 
of early writers.* The more practical directions occasion- 
ally to be met with in the treatises of Leon Battista Alberti, 
Leonardo da Vinci and others^ are conformable to the 
same system. Some Italian works> not written by painters, 
which pretend to describe this harmony, are, however, very 
imperfect, f A passage in Lodovico Doloe*s Dialogue on 
Colours is perhaps the only one worth quoting. '' He,'' 
says that writer, " who wishes to combine colours that are 
agreeable to the eye, will put grey next dusky orange ; yel- 
k)w-green next rose-colour ; blue next orange ; dark purple, 
black, next dark-green ; white next black, and white next 
flesh-colour."! The Dialogue on Painting, by the same 
author, has the reputation of containing some of Titian's 
precepts : if the above passage may be traced to the same 
source, it must be confessed that it is almost the only one of 
the kind in the treatise from which it is taken. 

NOTE D.— Par. GG. 
In some of these cases there can be no doubt that Goethe 



* Vasari obienres, " L'unione nella pittura d una discoitUiiia di colon 
divcni accordati insidme." — ^Vol. i. c. 18. This observation is repeated by 
various writers on art in nearly the same words, and at last appears in San- 
drart : ** Concordia, potissimum picturse decus, in discordift consistit, et quasi 
litigio colorum.'' — P. 1. c. 5. The source, perhaps, is Aristotle : he observer, 
'< We are delighted with harmony, because it is the union of contrary princi- 
ples having a ratio to each other." — Problem, 

t See *< Occolti Trattato de* Colon." Parma, 1568. 

\ **Volendo Tuomo accoppiare inside colon che all'occhio dilettino— 
porri insidme il berrettino col leonato ; il verde-giallo con Tincaxnato e roeM> ; 
il turchino con Parangi ; il morello col verde oscuro ; il nero col bianco ; il 
bianco con Pincamato." — Dialogo di 3f . Lodovico Doice n»i qua/9 ti ragioma 
della qua/itOf divtrnta, # proprieta dt* coiori, Venezia, 1365. 



Digitized by 



Google 



NOTES. 363 

attributes the contrast too exclusiTely to the physiological 
cause^ without making sufficient allowance for the actual 
diCTerence in the colour of the lights. The purely physical 
nature of some coloured shadows was pointed out by Pohl- 
mann; and Dr. Eckermann took some pains to convince 
Goethe of the necessity of making such a distinction. 
'Groethe at first adhered to his extreme view, but some time 
afterwards confessed to Dr. Eckermann^ that in the case of 
the blue shadows of snow (74), the reflection of the sky 
was undoubtedly to be taken into the account. ''Both 
causes may> however, operate together," he observed, *' and 
the contrast which a warm yellow light demands may 
heighten the effect of the blue.*' This was all his opponent 
contended.* 

With a few such exceptions, the general theory of Goethe 
with regard to coloured shadows is undoubtedly correct ; 
the experiments with two candles (68), and with coloured 
glass and fluids (80), as well as the observations on the 
shadows of snow (75), are conclusive, for in all these cases 
only one light is actually changed in colour, while the other 
still assumes the complemental hue. '' Coloured shadows,*' 
Dr. J. Midler observes, " are usually ascribed to the phy- 
siological influence of contrast ; the complementary colour 
presented by the shadow being regarded as the effect of 
internal causes acting on that part of the retina, and not of 
the impression of coloured rays from without. This expla- 
nation is the one adopted by Rumford, Goethe, Grotthuss, 
Brandes, Tourtual, Pohlmann, and most authors who have 
studied the subject.**f 

In the Historical Part the author gives an account of a 
scarce French work, " Observations sur les Ombres Colo- 
rees,'.' Paris, 1782. The writer J concludes that " the colour 

^ Eckennann's '* OesprMche mit Goethe," vol. ii. p. 76 and 280. 
t *' Elements of Physiology,** by J. MitUer, M.D., translated from the Ger* 
man by William Baly, M.D. London, 1839. 

X Anonymous, having only given the initials H. F* T. 



Digitized by 



Google 



364 NOTES. 

of shadows is as much owing to the light that causes them 
as to that which (more faintly) illumines them/* 

NOTE E— Par. 69. 

This opinion of the author is frequently repeated (201, 
dl2> 591)> and as it seenu at first sight to be at variance 
with a received principle of art> it may be as well at once to 
examine it. 

In order to see the general proposition in its true point 
of view> it will be necessary to forget the arbitrary distinc- 
tions of light and shade^ and to consider all such modifica- 
tions between highest brightness and absolute darkness only 
as so many lesser degrees of light.* The author, indeed, 
by the word shadow, always understands a lesser light. 

The received notion, as stated by Du Fresnoy,f is much 
too positive and unconditional, and is only true when we 
understand the 'displaying" light to comprehend certain 
d^rees of half or reflected light, and the '^ destroying" 
shade to mean the intensest degree of obscurity. 

There are degrees of brightness which destroy colour as 
well as degrees of darkness.^ In general, colour resides in 
a mitigated light, but a very little observation shows us that 
different colours require different degrees of light to display 
them. Leonardo da Vinci frequently inculcates the general 
principle above alluded to, but he as frequently qualifies it ; 
for he not only remarks that the highest light may be com- 

* Leonardo da Vinci observes : ** Uombra d diminuiione di luce, tenebre d 
privazione di luce.*' And again : " Sempre il minor lume d ombra del lume 
maggiore."— rra«a/o della Piltura, pp. 274-299. 

N. B. The fame edition before described baa been consulted tfirougbout. 
f ** Lux varium vivumque dabit, nullum umbra colorem." 

D« Arte GrapMici, 
'* Know first that ligbt displays and shade destroys 
Refulgent nature's variegated dies.*' — Mason's Trant/aiiom, 
I A Spanish writer, Diego de Carvalho e Sampayo, quoted by Ooetfae (** Far- 
beulehre," vol. ii.}, has a similar observation. This destroying effect of light 
is striking in climates where the sun is powerftil, and was not likely to escape 
the notice of a Spaniard. 



Digitized by 



Google 



NOTES. 365 

parative privation of colour, but observes, with great truth, 
that some hues are best displayed in their fully illumined 
parts, some in their reflections, and some in their half- 
lights ; and again, that every colour is most beautiful when 
lit by reflections from its own surface, or from a hue similar 
to its own.* 

The Venetians went further than Leonardo in this view 
and practice ; and he seems to allude to them when he cri- 
ticises certain painters, who, in aiming at clearness and 
fulness of colour, neglected what, in his eyes, was of supe- 
rior importance, namely, gradation and force of chiaro- 
scuro.+ 

That increase of colour supposes increase of darkness, as 
so often stated by Goethe, may be granted without difficulty. 
To what extent, on the other hand, increase of darkness, or 
rather diminution of light, is accompanied by increase of 
colour, is a question which has been variously answered by 
various schools. Examples of the total negation of the 
principle are not wanting, nor are they confined to the in- 
fancy of the art. Instances, again, of the opposite tendency 
are frequent in Venetian and early Flemish pictures resem- 
bling the augmenting richness of gems or of stained glass i^ 

* Trattato, pp. 103, 121, 123, 324, &c. 

t lb. pp. 85, 134. 

I Absolute opacity, to jud^ from the older ■pecimens of Btained glass, 
leems to have been considered inadmissible. The window was to admit light, 
however modified and varied, in the. form prescribed by the architect, and 
that form was to be preserved. This has been unfortunately lost sight of in 
some modem glass-painting, which, by excluding the light in large masses, 
and adopting the opacity of pictures (the reverse of the influence above al- 
luded to), has interfered with the i^chitectural symmetry in a manner far 
^m desirable. On the other hand, if we suppose painting at any period to 
have aimed at the imitation of stained glass, such an imitation must of neces- 
sity have led to extreme force ; for the painter sets out by substituting a mere 
white ground for the real light of the sky, and would thus be compelled to 
subdue every tone accordingly. In such an imitation his colour would soon 
deepen to its intensest state ; indeed, considerable portions of the darker hues 
would be lost in obscurity. The early Flemish pictures seldom err on the side 
of a gay superabundance of colour ; on the contrary, they are generally re- 



Digitized by 



Google 



366 NOTES. 

indeed, it is not impossible that the increase of colour in 
shade, which is so remarkable in the pictures alluded to, 
may have been originally suggested by the ridi and fiBsci- 
nating effect of stained glass ; and the Venetians, in this as 
in many other respects, may have improved on a hint bor- 
rowed from the early German painters, many of whom 
painted on glass.* 

At all events, the principle of still increasing in colour in 
certain hues seems to have been adopted in Flanders and in 
Venice at an early period ;f while Giorgione, in carrying 
the style to the most daring extent, still recommended it by 
corresponding grandeur of treatment in other respects. 

The same general tendency, except that the technical 
methods are less transparent, is, however, very striking in 
some of the painters of the school of Umbria, the instruc> 
tors or early companiims of Raphael. j: The influence of 

markable for comparatiTely cool lights, for extreme depth, and a certain cub- 
dned splendour, qualities which would necessarily result from the imitation or 
influence in question. 

* See Langlois, ** Peinture sur Verre." Rouen, 1832 ; Descamps, « La Vie 
des Peintret Flamauds ;" and Gessert, *< Oeschichte der Olasmalerei." Stwt- 
gard, 1839. The antiquity of the glass manufactory of Murano (Venice) is also 
not to be forgotten. Vasari objects to the Venetian glass, because it was darker 
in colour than that of Flanders, France, and England ; but this very quality 
was more likely to hare an advantageous influence on the style of the early oil- 
painters. The use of stained glass was, however, at no period very general in 
Italy. 

t Zanetti, " Delia Pittura Veneiiana," marks the progress of the early Ve- 
netian painters by the gradual use of the warm outline. There are somw 
mosaics in St. Mark's which have the effect of flesh-colour, but on examina- 
tion, the only red colour used is found to be in the outlines and markings. 
Many of the drawings of the old masters, heightened with red in the shadows, 
have the same effect. In these drawings the artists judiciously avoided co- 
louring the lips and cheeks much, for this would only have betrayed the want 
of general colour, as is observable when statues are so treated. 

I Andrea di Luigi, called L'Ingegno, and Nicecdo di F^iUgno, are cited as 
the most prominent examples. See Rmnohr, ** Italienische Forschungen.*' 
Peragino himself occasionally adopted a very glowing colour. 

The early Italian schools which adhered most to the Byiantine types appear 
to have been also the most remarkable for depdi, or rather darkness, of colour. 
This fidelity to customary representation wan sometimes, as in the schools of 



Digitized by 



Google 



NOTES. 367 

these examples, as well as that of Fra Bartolommeo, in 
Florence^ is distinctly to be traced in the works of the great 
artist just named^ but neither is so marked as the effect of 
his emulation of a Venetian painter at a later period. The 
glowing colour^ sometimes bordering on exaggeration* which 
Raphael adopted in Rome, is undoubtedly to be attri- 
buted to the rivalry of Sebastian del Piombo. This painter, 
the best of Giorgione*s imitators, arrived in Rome, invited 
by Agostini Chigi, in 151 1, and the most powerful of Ra« 
phaeFs frescoes, the Heliodorus and Mass of Bolsena, as 
well as some ix>rtrait8 in the same style, were painted in the 
two following years. In the hands of some of RaphaeVs 
scholars, again, this extreme warmth was occasionally car- 
ried to excess, particularly by Pierino del Vaga, with whom 
it often d^enerated into redness. The representative of 
the glowing manner in Florence was Fra Bartolommeo, and, 
in the same quality, considered abstractedly, some painters 
of the school of Ferrara were second to none. 

In another Note (par. 177) some further considerations 



Umbria, and to a certain extent in those of Siena and Bologna, the result of 
a religious veneration for the ancient examples ; in others, as in Venice, the 
circumstance of frequent intercourse with the Lerant is also to be taken into 
the account. The Greek pictures of the Madonna, not to mention other repre* 
sentations, were extremely dark, in exaggerated conformity, it is supposed, 
with the tradition respecting her real complexion (see IVAgincourt, vol. iv. 
p. 1) ; a belief which obtained so late as Lomasso's time, for, speaking of the 
Madonna, he obsenres, ** Leggesi perd che (a alquanto bruna.*' Oiotto, who 
with the independence of genius betrayed a certain contempt for these tradi- 
tions, failed perhaps to unite improvement with novelty when he substituted a 
pale white flesh-colour for the traditional brown. Some specimens of his 
works, still existing at Padua, present a remarkable cqptrast in thu respect 
with the earliest productions of the Venetian and Paduan artists. His works 
at Florence differ as widely firom those of the earlier painters of Tuscany. 
This peculiarity was inherited by his imitators, and at one time almost chairac- 
terised the Florentine school. Leon Battista Albert! was not perhaps the 
first who objected to it (*' Vorrei io che dai pittori fbsse comperato il color 
bianco assai piil caro che le presiosissime gemme."^/>e//a PHiura^ 1. ii.) 
The attachment of Fra Barlolommeo to the grave character of the Christian 
types is exemplified in his deep colouring, as well as in other req>ects. 



Digitized by 



Google 



368 NOTES. 

are offered, which may partly explain the prevalence of this 
style in the beginning of the sixteenth century; here we 
merely add, that the conditions under which the appearance 
itself is most apparent in nature are perhaps more obvious 
in Venice than elsewhere. . The colour of general nature 
may be observed in all places with almost equal conve- 
nience, but with regard to an important quality in living 
nature, namely, the colour of flesh, perhaps there are no 
circumstances in which its effects at different distances can 
be so conveniently compared as when the observer and the 
observed gradually approach and glide past each other on 
so smooth an element and in so undisturbed a manner as 
on the canals and in the gondolas of Venice ;* the com- 
plexions, from the peculiar mellow carnations of the Italian 
women to the sun-burnt features and limbs of the mariners, 
presenting at the same time the fullest variety in another 
sense. 

At a certain distance — the colour being always assumed 
to be unimpaired by interposed atmosphere — the reflections 
appear kindled to intenser warmth ; the fiery glow of Gior- 
gione is strikingly apparent ; the colour is seen in its largest 
relation ; the nuicchia,^ an expression so emphatically used 
by Italian writers, appears in all its quantity, and the re- 
flections being the focus of warmth, the hue seems to 
deepen in shade. 

A nearer view gives the detail of cooler tints more per- 
ceptibly,;]: and the forms are at the same time more distinct 
Hence Lanzi is quite correct when, in distingmshing the 
style of Titian from that of Giorgione, he says that Titian*s 



* Holland might be excepted, and in Holland similar causes may have 
had a similar influence. 

t Local colour ; literally, the biot, 

X Zanetti ventures to single out the picture of Tobit and the Angel in S. 
Maniale as the first example of Titian's own manner, and in which a direct 
imitation of Giorgione is no longer apparent. In this picture the lights are 
cool and the blood-tint very effective. 



Digitized by 



Google 



NOTES. 309 

was at once more defined and less fiery.* In a still nearer 
observation the eye detects the minute lights which Leo- 
nardo da Vinci says are incompatible with efiects such as 
those we have described^f and which, accordingly, we never 
find in Giorgione and Titian. This large impression of 
colour, which seems to require the condition of comparative 
distance for its full effect, was most fitly employed by the 
same great artists in works painted in the open air or for 
large altar-pieces. Their celebrated frescoes on the exterior 
of the Fondaco de' Tedeschi at Venice, to judge from their 
faint remains and the descriptions of earlier writers, were 
remarkable for extreme warmth in the shadows. The old 
frescoes in the open air throughout Friuli have often the 
same character, and, owing to the fulness of effect which this 
treatment ensures, are conspicuous at a very great distance. J; 
In assuming that the Venetian painters may have ac- 
quired a taste for this breadth§ of colour under the circum- 
stances above alluded to, it is moreover to be remembered 
that the time for this agreeable study was the evening; 
when the sun had already set behind the hills of Bassano ; 
when the light was glowing but diffused; when shadows 

♦ ** Meno slUmato, men focoao." — Storia Pittcricfi, 

t " La prima cosa che de' color! si perde nolle distanxe d il liutro, loro mi- 
nima parte." — 7Va//o/o,p. 213 ; and elsewhere, " I lumi principal! in picciol 
luogo son quelli che in picciola distanza sono i primi che si perdono all' occhio." 
—p. 128. 

X A colossal St. Christopher, the usual subject, is frequently seen occupying 
the whole height of the external wall of a church. We have here an example 
of the influence of religion, such as it was, even on the style of colouring and 
practical methods of the art. The mere sight of the image of St. Christopher, 
the type of strength, was considered sufficient to reinvigorate those who were 
exhausted by the labours of husbandry. The following is a specimen of the 
inscriptions inculcating this belief : — 

" Christophori Sancti speciem quicumque tuetur, 
nio namque die nullo languore tenetur." 
Hence the practice of painting the figure on the outside of churches, hence its 
colossal size, and hence the powerful qualities in colour above described. See 
Maniago, ** Storia delle Belle Arti Friulane." 

( The authority of Fuseli sufficiently warrants the application of the term 
breadth to colour ; he speaks of Titian's ** breadth of local tint." 

2 B 



Digitized by 



Google 



370 NOTES. 

were soft— conditions all agreeing with the character of 
their colouring:* above all, when the hour invited the 
fairer portion of the population to betake themselves in 
their gondolas to the lagunes. The scene of this '* prome- 
nade'' was to the north of Venice, the quarter in which 
Titian at one time lived. A letter exists written by Fran- 
cesco Priscianese, giving an account of his supping with 
the great painter in company with Jacopo Nardi, Pietro 
Aretino> the sculptor Sansovino, and others. The writer 
speaks of the beauty of the garden, where the table was 
prepared, looking over the lagunes towards Murano, ** which 
part of the sea,'* he continues, ''as soon as the sun was 
down, was covered with a thousand gondolas^ graced with 
beautiful women, and enlivened by the harmony of voices 
and instruments, which lasted till midnight, forming a 
pleasing accompaniment to our cheerful repast, "f 

To return to Goethe : perhaps the foregoing remarks may 
warrant the conclusion that his idea of colour in shadow is 
not irrecondleable with the occasional practice of the best 
painters. The highest examples of the style thus defined 
are, or were, to be found in the works of GiorgioneJ and 
Titian, and hence the style itself, though " within that circle" 

K 

* Zanetti quotes an opinion of the painters of his time to the same effect : — 
" Teneano essi (alcimi maestri) per cosa certa, che in molte opcre Tiziauo 
Tclesse fingere il lume— quale si vede nell' inclinarsi del sole verso la sera. 
Oli orizzonti assai luminosi dietro le montagne, le ombre incerte e pid le car- 
nagioni brunette e rosseggianti delle figure, grinduceano a cfeder questo.'' — 
Lib. ii. Leonardo da Vinci observes, ** Quel corpo che si trover^ in mediocre 
lume fia in lui poca differenza da' lumi all' ombre. E questo accade sul far 
dclla sera — e queste opere sono dolci ed hacci grazia ogni qualiti di volto,*' 
&c. — ^p. 336. Elsewhere, ** Le ombre fatte dal sole od altri lumi particolari 
sono senza grazia." — ^p. 357 ; see also p. 247. 

f See " Francesco Priscianese IV Primi Principii della Lingua Latina," 
Venice, 1550. The letter is at the end of the work. It is quoted in Ticozzi^s 
« Vite de' Pittori Vecelli," Milan, 1817. 

I The works of Qiorgione are extremely rare. The pictures best calculated 
to give an idea of the glowing manner for which he is celebrated, are the 
somewhat early works and several of the altar-pieces of Titian, the l>e«t 
specimens of Palma Vecchio, and the portraits of Sebastian del Piombo. 



Digitized by 



Google 



NOTES. 37 1 

few ^' dare walk/* is to be considered the grandest and most 
perfect. Its possible defects or abuse are not to be dis- 
sembled : in addition to the danger of exaggeration "^ it is 
seldom united with* the plenitude of light and shade, or 
with roundness ; yet^ where fine examples of both modes of 
treatment may be compared^ the charm of colour has per- 
haps the advantage, f The difficulty of uniting qualities so 
different in their nature, is proved by the very rare instances 
in which it has been accomplished. Tintoret in endeavour- 
ing to add chiaro-scuro to Venetian colour, in almost every 
instance fell short of the glowing richness of Titian.J 

* Zanetti and Lodovico Dolce mention Lorenio Lotto as an instance of the 
excess of Gioigione's style. Titian himself sometimes overstepped the mark, 
as his biographers confess, and as appears, among other instances, from the 
head of St. Peter in the picture (now in the Vatican) in which the celebrated 
St. Sebastian is introdaeed. Raphael was criticised by some cardinals for a 
similar defect. See " Gastiglione, 11 Cortigiano,'' 1. ii. 

In the same paragraph to which the present observations refer, the authority 
of Kircher is quoted ; his treatise, ** Ars magna lucis et umbrae,'' was published 
in Rome in 1646. In a portrait of Nicholas Poussin, engraved by Clouet, the 
painter b represented holding a book, which^ from the title and the circum- 
stance of Poussin having lived in Rome in lurcher's time, Ooethe supposes to 
be the work in question. The abuse of the principle above alluded to, is per- 
haps exemplified in the red half-tints observable in some of Poussin's figures. 

The augmentation of colour in subdued light was still more directly taught 
by Lomaso. He composes the half-tints of flesh merely by diminishing the 
quantity of white, the proportions of the other colours employed (for he enters 
into minute details) remaining unaltered. See his ** Trattato della arte della 
Pittura," Milan, 1584, p. 301. 

f In the Dresden Ghdlery, a picture attributed to Titian — at all events a 
lucid Venetian picture — hangs next the St. George of Correggio. After 
looking at t^e latter, the Venetian work appears glassy and unsubstantial, but 
on reversing the order of comparison, the Correggio may be said to suffer more, 
and for a moment its fine transitions of light and shade seem changed to 
heaviness. 

X The finest works of Tintoret— the Crucifixion and the Miracolo del Servo 
(considered here merely with reference to*" their colour,) may be said to 
combine the excellences of Titian and Oiacomo Bassan, on a grand scale ; the 
sparkling clearness of the latter is one of the prominent characteristics of 
these pictures. Tintoret is reported to have once said fhat a union of his own 
knowledge of form with Bassan's colour would be the perfection of pamting. 
See " Verci Notisie de» Pittori di Bassano ;" Ven. 1775, p. 61. % 

2 b2 



Digitized by 



Google 



372 NOTES. 

Giacomo Bassan and his imitators, even in their dark effects, 
still had the principle of the gem in view : their light, in 
certain hues, is the minimum of colour, their lower tones are 
rich, their darks intense, and all is sparkling."^ Of the great 
painters who, beginning, on the other hand, with chiaro- 
scuro, sought to combine with it the full richness of colour, 
Correggio, in the opinion of many, approached perfection 
nearest ; but we may perhaps conclude with greater justice 
that the desired excellence was more completely attained by 
Rembrandt than by any of the Italians. 

NOTE F— Par. 83. 

The author, in these instances, seems to be anticipating 
his subsequent explanations on the effect of semi-transparent 
mediums. For an explanation of the general view contained 
in these paragraphs respecting the gradual increase of co- 
lour from high light, see the last Note. 

The anonymous French work before alluded to, among 
other interesting examples, contains a chapter on shadows 
cast by the upper light of the sky and coloured by the 
setting sun. The effect of this remarkable combination is, 
that the light on a wall is most coloured immediately under 
a projecting roof, and becomes comparatively neutralised in 
proportion to its distance from the edge of the darkest shade. 

NOTE G.— Par. 98. 

'* The simplest case of the phenomenon, which Goethe 
calls a subjective halo, and one which at once explains its 
cause, is the following. Regard a red wafer on a sheet of 
white paper, keeping the eye stedfastly fixed on a point at 

• That this last quality, the characteristic of Bassan's best pictures, was 
held in high estimation by Paul Veronese, is not only endent irom that 
painter's own works, but from the circumstance of his preferring to place his 
sons with Bassan rather than with any other painter. (See " Boschini Carta del 
Navegar," p. 280.) The Baptbm of Sta. Lucilla, in Boschini's time con- 
sidered the finest of Qiacomo's works, is still in the church of S. Valentino, at 
Baasano, and may be considered the type of the lucid and sparkling manner. 



Digitized by 



Google 



NOTES. 373 

its center. When the retina is fatigued^ withdraw the head 
a little from the paper, and a green halo will appear to sur- 
round the wafer. By this slight increase of distance the 
image of the wafer itself on the retina becomes smaller, and 
the ocular spectrum which before coincided with the direct 
image, being now relatively larger, is seen as a surrounding 
ring.'* — S. F. Goethe mentions cases of this kind, but does 
not class them with subjective halos. See Par. 30. 

NOTE H.— Par. 113. 

'* Cases of this kind are by no means uncommon. Several 
interesting ones are related in Sir John Herschell's article on 
Light in the Encyclopaedia Metropolitana. Careful inves- 
tigation has, however, shown that this defect of vision arises 
in most, if not in all cases, from an inability to perceive the 
red, not the blue rays. The terms are so confounded by the 
individuals thus affected, that the comparison of colours in 
their presence is the only criterion." — S. F. 

NOTE I.— Par. 135. 

The author more than once admits that this chapter on 
'< Pathological Colours" is very incomplete, and expresses a 
wish (Par. 734) that some medical physiologists would in- 
vestigate the subject further. This was afterwards in a 
great degree accomplished by Dr. Johannes Muller, in his 
memoir ** Uber die Phantastischen Gesichtserscheinungen." 
Coblentz, 1826. Similar phenomena have been also in- 
vestigated with great laboiur and success by Purkinje. For 
a collection of extraordinary facts of the kind recorded by 
these writers, the reader may consult Scott's Letters on 
Demonology and Witchcraft.* The instances adduced by 
Muller and others are, however, intended to prove the in- 
herent capacity of the organ of vision to produce light and 
colours. In some maladies of the eye, the patient, it seems, 

* See also a curious passage on the beatific vision of the monks of Mount 
Athos, in Gibbon, chap. 63. 



Digitized by 



Google 



374 NOTES. 

suffers the constant presence of light without external light. 
The exciting principle in this case is thus proved to be 
within, and the conclusion of the physiologists is that ex- 
ternal light is only one of the causes which produce lumin- 
ous and coloured impressions. That this view was antici- 
pated by Newton may be gathered from the concluding 
*' query" in the third book of his Optics. 

NOTE K.— Par. 140. 

'' Catoptrical colours. The colours included under this 
head are principally those of fibres and grooved surfaces ; 
they can be produced artificially by cutting parallel grooves 
on a surface of metal from 2000 to 10^000 in the inch. See 
* Brewster's Optics/ p 120. The colours called by Goethe 
paropHccU, correspond with those produced by the difiraction 
or inflection of light in the received theory. — See Brewster, 
p. 95. The phenomena included under the title * Epop- 
tical Colours/ are generally known as the colours of thin 
plates. They vary with the thickness of the film, and the 
colour seen by reflection always differs from that seen by 
transmission. The laws of these phenomena have been 
thoroughly investigated. See Nobili, and Brewster, p. 100." 
— S. F. 

The colours produced by the transmission of polarised 
light through chrystalised mediums, were described by 
Goethe, in his mode, subsequently to the publication of his 
general theory, under the name of Entoptic Colours. See 
note to Par. 485. 

NOTE L.— Par. 150. 

We have in this and the next paragraph the outline of 
Goethe's system. The examples that follow seem to es- 
tablish the doctrine here laid down, but there are many 
cases which it appears cannot be explained on such prin- 
ciples : hence, philosophers generally prefer the theory of 
absorption, according to which it appears that certain 
mediums ** have the property of absorbing some of the corn- 



Digitized by VjOOQ IC 



NOTES. 375 

ponent rays of white lights while they allow the passage of 
others."* 

Whether all the facts adduced by Goethe — for instance, 
that recorded in Par. 172, are to be explained by this doc- 
trine^ we leave to the investigators of nature to determine. 
Dr. Eckermann, in conversing with Goethe, thus described 
the two leading phenomena (156, 158) as seen by him in the 
Alps. ^* At a distance of eighteen or twen^ miles at mid- 
day in bright sunshine, the snow appeared yellow or even 
reddish, while the dark parts of the mountain, free from 
snow, were of the most decided blue. The appearances 
did not surprise me, for I could have predicted that the 
mass of the interposed medium would give a deep yellow 
tone to the white snow, but I was pleased to witness the 
effect, since it so entirely contradicted the erroneous views of 
some philosophers, who assert that the air has a blue-iinging 
quality. The observation, said Goethe, is of importance, 
and contradicts the error you allude to completely."' f 

The same writer has some observatious to the same effect 
on the colour of the Rhone at Geneva. A circumstance of 
an amusing nature which he relates in confirmation of 
Goethe*s theory, deserves to be inserted. *' Here (at 
Strasburg), passing by a shop, I saw a little glass bust of 
Napoleon, which, relieved as it was against the dark in- 

* See ** Muller*8 Elemente of Physiology," tranftlated from the Oenuan by 
William Baly, M.D. "The laws of absorption," it has beeu observed, 
«< have not been studied with so much success as those of other phenomena of 
physical optics, but some excellent observations on the subject will be found 
in HerschelPs Treatise on Light in the Encyclopaedia Metropolitana, J III." 

t " Eckermann's GesprSche mit Ooethe," vol. ii. p. 280. Leonardo da Vinci 
had made precisely the same observation. ** A distant mountain will appear 
of a more beautiful blue in proportion as it is dark in colour. The illumined 
air, interposed between the eye and the dark mass, being thinner towards the 
summit of the mountain, will exhibit the darkness as a deeper blue and vice 
vertd,** — Trattato delia Pittura, p. 143. Elsewhere — ** The air which in- 
tervenes between the eye and dark mountains becomes blue *, but it dues not 
become blue in (before) the light part, and much less in (before) the {lortion 
that is covered with snow." — p. 244. 



Digitized by 



Google 



376 NOTES. 

tenor of the room, exhibited every gradation of blue, from 
milky light blue to deep violet. I foresaw that the bust 
seen from within the shop with the light behind it, would 
present every degree of yellow^ and I could not resist walk- 
ing in and addressing the owner, though perfectly unknown 
to me. My first glance was directed to the bust, in which, 
to my great joy, I saw at once the most brilliant colours of 
the wanner kind, from the palest yellow to dark ruby red. 
I eagerly asked if I might be allowed to purchase the bust ; 
the owner replied that he had only lately brought it with 
him from Paris, from a similar attachment to the emperor 
to that which I appeared to feel^ but, as my ardour seemed 
far to surpass his, I deserved to possess it. So invaluable 
did this treasure seem in my eyes, that I could not help 
looking at the good man with wonder as he put the bust into 
my hands for a few franks. I sent it, together with a curious 
medal which I had bought in Milan, as a present to Groethe, 
and when at Frankfort received the following letter from 
him." The letter, which Dr. Eckermann gives entire, thus 
concludes — " When you return to Weimar you shall see 
the bust in bright sunshine, and while the transparent 
countenance exhibits a quiet blue,* the thick mass of the 
breast and epaulettes glows with every gradation of warmth, 
from the most powerful ruby-red downwards; and as the 
granite statue of Memnon uttered harmonious sounds, so the 
dim glass image displays itself in the pomp of colours. The 
hero is victorious still in supporting the Farbenlehre.**f 

One effect of Goethe's theory has been to invite the at- 
tention of scientific men to facts and appearances which 
had before been unnoticed or unexplained. To the above 
cases may be added the very common, but very important, 
fact in painting, that a light warm colour, passed in a semi- 

* This supposes either that the mass was considerably thicker, or that there 
was a dark ground behind the head, and a light ground behind the rest of the 
figure. 

t " Eckermann^s Gesprache mit Goethe," vol. ii. p. 242. 



Digitized by 



Google 



NOTES. 377 

transparent state over a dark one, produces a cold, bluish 
hue, while the operation reversed, produces extreme warmth. 
On the judicious application of both these effects, but espe- 
cially of the latter, the richness and brilliancy of the best- 
coloured pictures greatly depends. The principle is to be 
realised in the productions of schools apparently oppo- 
site in their methods. Thus the practice of leaving the 
ground, through which a light colour is apparent, as a 
means of ensuring warmth and depth, is very common 
among the Dutch and Flemish painters. The Italians, 
again, who preferred a solid under-painting, speak of in- 
ternal light as the most fascinating quality in colour. When 
the ground is entirely covered by solid painting, as in the 
works of some colourists, the warmest tints in shadows and 
reflections have been found necessary to represent it. This 
was the practice of Rembrandt frequently, and of Reynolds 
universally, but the glow of their general colour is still 
owing to its being repeatedly or ultimately enriched on the 
above principle. Lastly, the works of those masters who 
were accustomed to paint on dark grounds are often heavy 
and opaque ; and even where this influence of the ground 
was overcome, the effects of time must be constantly dimi- 
nishing the warmth of their colouring as the surface be- 
comes rubbed and the dark ground more apparent through 
it. The practice of painting on dark grounds was intended 
by the Carracci to compel the students of their school to aim 
at the direct imitation of the model, and to acquire the use 
of the brush ; for the dark ground could only be overcome 
by very solid painting. The result answered their expecta- 
tions as far as dexterity of pencil was concerned, but the 
method was fatal to brilliancy of colour. An intelligent 
writer of the seventeenth century* relates that Guido adopted 
his extremely light style from seeing the rapid change in 
some works of the Carracci soon after they were done It 

* Scanelli, " Microcoamo della Pittura," Cetena, 1657, p. 114. 



Digitized by 



Google 



378 NOTES. 

is important^ however, to remark, that Guido's remedy was 
external rather than internal brilliancy; and it is evident 
that so powerless a brightness as white paint can only ac- 
quire the splendour of light by great contrast, and, abore 
all, by being seen through external darkness. The secret 
of Van Eyck and his contemporaries is always assumed to 
consist in the vehicle (varnish or oils) he employed ; but a 
far more important condition of the splendour of colour in 
the works of those masters was the careful preservation of 
internal light by painting thinly, but ultimately with great 
force, on white grounds. In some of the early Flemish 
pictures in the Royal Gallery at Munich, it may be ob- 
served, that wherever an alteration was made by the painter, 
so that a light colour is painted over a dark one, the colour 
is as opaque as in any of the more modem pictures which 
are generally contrasted with such works. No quality in 
the vehicle could prevent this opacity under such circum- 
stances; and on the other hand, provided the internal 
splendour is by any means preserved, the vehicle is oompara* 
tively unimportant. 

It matters not (say the authorities on these points) whe- 
ther the effect in question is attained by painting thinly 
over the ground, in the manner of the early Flemish painters 
and sometimes of Rubens, or by painting a solid light pre- 
paration to be afterwards toned to richness in the manner of 
the Venetians. Among the mechanical causes of the clear- 
ness of colours superposed on a light preparation may be 
mentioned that of careful grinding. All writers on art who 
have descended to practical details have insisted on this. 
From the appearance of some Venetian pictures it may be 
conjectured that the colours of the solid under-painting 
were sometimes less perfectly ground than the scumbling 
colours (the light having to pass through the one and to be 
reflected from the other). The Flemish painters appear to 
have used carefully-ground pigments universally. This is 
very evident in Flemish copies from Raphael, which, though 



Digitized by 



Google 



NOTES. 379 

equally impasted with the originals, are to be detected, among 
other indications, by the finely-gromid colours employed 

NOTE M.— Par. 177. 

Without entering further into the scientific merits or de- 
merits of this chapter on the '' First Class of Dioptrical 
Colours/' it is to be observed that several of the examples 
correspond with the observations of Leonardo da Vinci, 
and again with those of a much older authority^ namely, 
Aristotle. Goethe himself admits, and it has been remarked 
by others, that his theory, in many respects, closely resem* 
bles that of Aristotle: indeed he confesses* that at one 
time he had an intention of merely paraphrasing that philo- 
sopher's Treatise on Colours.f 

We have already remarked (Note on par. 150) that 
Goethe*s notion with regard to the production of warm 
colours, by the interposition of dark transparent mediums 
before a light ground, agrees with the practice of the best 
schools in colouring ; and it is not impossible that the same 
reasons which may make this part of the doctrine generally 
acceptable to artists now, may have recommended the very 
similar theory of Aristotle to the painters of the fifteenth 
and sixteenth centuries : at all events, it appears that the 
ancient theory was known to those painters* 

It is unnecessary to dwell on the fact that the doctrines 
of Aristotle were enthusiastically embraced and generally 
inculcated at the period in question ;X but it has not been 

• ''OMchichteder Farbenlefare," in the ** N^hgelasaene Werke." Gotta, 
1833. 

f The treatise in quention is ascribed by Ooethe to Theophrastus, but it is 
included in most editions of Aristotle, and even attributed to him in those 
which contain the works of both philosophers ; for instance, in the Aldine 
Princeps edition, 1496. Calcagnini says, the treatise is made up of two sepa- 
rate works on the subject, both by Aristotle. 

I His authority seems to have been equally great on subjects connected 
with the phenomena of vision : the Italian transUtor of a Latin treatise, by 
Fortius, on the structure and colours of the eye, thus o^m his dedication to 
the Cardinal Ercole Oonsaga, of Mantua :—** Grande ana quasi infinito e 



Digitized by 



Google 



380 NOTES. 

observed that the Italian writers who translated, para- 
phrased, and commented on Aristotle*s Treatise on Colours 
in particular^ were in several instances the personal friends 
of distinguished painters. Celio Calcagnini* had the highest 
admiration for Raphael ; Lodovico Dolcef was the eulogist 
of Titian ; Portius,J whose amicable relations with the Flo- 
rentine painters may be inferred from various circumstances^ 
lectured at Florence on the Aristotelian doctrines early in 
the sixteenth century. The Italian translations were later, 
but still prove that these studies were undertaken with re- 
ference to the arts, for one of them is dedicated to the 
painter Cigoli.§ 

Tobligo che ha il mondo con quel piii divino che umaDO spirito di Aristo- 
tUe." 

* In a letter to Ziegler the mathematician, Calcag:nini speaks of Raphael 
as " the first of painters in the theory as well as in the practice of his art." 
This expression may, however, have had reference to a remarkable circum- 
stance mentioned in the same letter, namely, that Raphael entertained the 
learned Fabiusof Ravenna as a constant guest, and employed him to tranalat« 
Vitruviiis into Italian. This MS. translation, with marginal notes, written 
by Raphael, is now in the library at Munich. " Passavant, Rafael von Urbino.** 

f Lodovico Dolce's Treatise on Colours (1565) is in the form of a dialogue, 
like his ** Aretino." The abridged theory of Aristotle is followed by a trans- 
lation of the Treatise of Antonius Thylesiiu on Colours ; this is adapted to the 
same colloquial form, and the author is not acknowledged : the book ends 
with an absurd catalogue of emblems. The ** Somma della Filosofia d'Aria- 
totile,'' published earlier by the same author, is a very careless performance. 

I A Latin translation of Aristotle's Treatise on Colours, with comments by 
Simon Fortius, was first published, according to Goethe, at Naples in 1537. 
In a later Florentine edition, 1548, dedicated to Cosmo I., Fortius alludes to 
his having lectured at an earlier period in Florence on the doctrines of Aris- 
totle, at which time he translated the treatise in question. Another Latin 
translation, with notes, was published later in the same century at Padua — 
** Emanuele Marguino Interprete :*' but by far the clearest view of the Aristo- 
telian theory is to be found in the treatise of Antonio Vidi Scarmiglione of 
Fuligno C* De Coloribus," Marpurgi, 1591). It is dedicated to the Emperor 
Rudolph II. Of all the paraphrases of the ancient doctrine this comes nearest 
to the system of Qoethe ; but neither this nor any other of the works alluded 
to throughout this Note are mentioned by the author in his History of the 
Doctrine of Colours, except that of Fortius. 

§ An earlier Italian translation appeared in Rome, 1535. See ** Argelatus 
Biblioteca degli Volgariuatori." 



Digitized by 



Google 



NOTES. 381 

The writers on art> from Leon Battista Albert! to Bor- 
ghini, without mentioning later authorities, either tacitly 
coincide with the Aristotelian doctrine, or openly profess 
to explain it. It is true this is not always done in the 
clearest manner, and some of these writers might say with 
Lodovico Dolce, " I speak of colours, not as a painter, for 
that would be the province of the divine Titian.'* 

Leonardo da Vinci in his writings, as in everything else, 
appears as an original genius. He now and then alludes 
generally to opinions of " philosophers," but he quotes no 
authority ancient or modem. Nevertheless, a passage on 
the nature of colours, particularly where he speaks of the 
colours of the elements, appears to be copied from Leon 
Battista Alberti,* and from the mode in which some of 
Leonardo's propositions are stated, it has been supposed f 
that he had been accustomed at Florence to the form of the 
Aristotelian philosophy. At all events, some of the most 
important of his observations respecting light and colours, 
have a great analogy with those contained in the treatise in 
question. The following examples will be sufficient to 
prove this coincidence ; the corresponding passages in 
Goethe are indicated, as usual, by the numbers of the para- 
graphs; the references to Leonardo's treatise are given at 
the bottom of the page. 

Aristotle. 

'* A vivid and brilliant red appears when the weak rays of 
the sun are tempered by subdued and shadowy white." — 
154. 

Leonardo. 

" The air which is between the sun and the earth at sun- 



« «« Delia Pittura e della Statoa,'' Lib. 1, p. 16, Milan edition, 1804. Com- 
pare with the '* Trattato della Pittura,'' p. 141. Other pointi of resemblance 
are to be met with. The notion of certain colours appropriated to the four 
elements, occurs in Aristotle, and is indeed attributed to older writers. 

t See the notes to the Roman edition of the « Trattato della Pittura." 



Digitized by 



Google 



382 NOTES. 

rise or sun-set, always invests what is beyond it more than 
any other (higher) portion of the air : this is because it is 
whiter."* 

A bright object loses its whiteness in proportion to its 
distance from the eye much more when it is illuminated by 
the sun, for it partakes of the colour of the sun mingled with 
the colour (tempered by the mass) of the air interposed be- 
tween the eye and the brightness, f 

Aristotle. 

''If light is overspread with much obscurity, a red colour 
appears ; if the light is brilliant and vivid, this red changes 
to a flame-colour." J — 150, l60. 

Leonardo. 

'* This (the effect of transparent colours on various 
grounds) is evident in smoke^ which is blue when seen 
against black, but when it is opposed to the (light) blue 
sky, it appears brownish and reddening. "§ 

Aristotle. 

'' White surfaces as a ground for colours, have the effect 
of making the pigments|| appear in greater splendour." — 
594, 902. 



• Page 237. 

t Page 301 

X In the Treatise De Igne, by Thec^hrastus, we find the tamo notion thus 
preMed : " Brightness (t« Xwtuf) seen through a dark coloured medium 
(}ik TU ftiXafn) appears red ; as the sun seen through smoke or soot : hence 
the coal is redder than the flame." Scarmiglione, from whom Kircher seems 
to hare copied, observes: — **Itaque color realb est hiz opaca; licet id e 
plurimis apparentiis colligere. Luna enim in magnft solis eclipsi rubra con* 
spicitur, quia tenebris lux praepeditur ac veluti tegitur." — De Co/oribyt, 

i Page 122. 

II T^ AfSn : translated Jloret bj Calcagnini and the rest, by Goethe, die 
BKUh$, the bloom. That the word sometimes signified pigments is sofllciently 
apparent from the following passage of Suidas (qvoted by Bmerie Dwrid, ** Dis- 
couTs Historiques sur la Peinture Modeme'*) &^wi Mtu^finftU^ty M#f ^t^tfUim. 



Digitized by 



Google 



NOTES. 383 

Leonardo. 

" To exhibit colours in their beauty, the whitest ground 
should be prepared. I speak of colours that are (more or 
less) transparent."* 

Aristotle. 

" The air near us appears colourless ; but when seen in 
depth, owing to its thinness it appears blue ;f for where the 
light is deficient (beyond it), the air is affected by the dark- 
ness and appears blue : in a very accumulated state, how- 
ever, it appears, as is the case with water, quite white.*' — 
155, 158. 

Leonardo. 

*' The blue of the atmosphere is owing to the mass of 
illuminated air interposed between the darkness above and 
the earth. The air in itself has no colour, but assumes 
qualities according to the nature of the objects which are 
beyond it. The blue of the atmosphere will be the more 
intense in proportion to the degree of darkness beyond itf ' 
elsewhere — *' if the air had not darkness beyond it, it would 
be white. "J 

Aristotle. 

*' We see no colour in its pure state, but every hue is 
variously intermingled with others: even when it is unin- 
fluenced by other colours, the effect of light and shade 
modifies it in various ways, so that it undergoes alterations 
and appears unlike itself. Thus, bodies seen in shade or in 

fytiti Hui r$if iffrnt* Vaiiis pigmentis oniatsB,ut ceruss^ fuco, et aliis similibiis. 
(Suid. in voc. '£(«93ir/<fMM.) A panel prepared for painting, with a white 
ground consolidated with wax, and perhaps mastic, was found in Herculaneum. 
• Page 114. 

m^miimrm. " But when seen in depth, it i^pears (eren) in its nearest colour, 
blue, owing to its thinness.*' The Latin interpretations vary very much 
throughout. The point which is chiefly important is however plain enough, 
viz. that darkness seen through^ light medium is blue. 
I Page 136—430. 



Digitized by 



Google 



384 NOTES. 

light, in more pronounced or softer sun-shine, with their 
surfaces inclined this way or that, with eyery change exhibit 
a different colour." 

Leonardo. 

" No substance will ever exhibit its own hue unless the 
light which illumines it is entirely similar in colour. It very 
rarely happens that the shadows of opaque bodies are really 
similar (in colour) to the illumined parts. The surface 
of every substance partakes of as many hues as are reflected 
from surrounding objects."* 

Aristotle. 

'' So, again, with regard to the light of (ire, of the moon, 
or of lamps, each has a different colour, which is variously 
combined with differently coloured objects." 

Leonardo. 

" We can scarcely ever say that the surface of illumined 
bodies exhibits the real colour of those bodies. Take a 
white band and place it in the dark, and let it receive light 
by means of three apertures from the sun, from fire, and 
from the sky : the white band will be tricoloured."f 

Aristotle. 

" When the light falls on any object and assumes (for 
example) a red or green tint, it is again reflected on other 
substances, thus undergoing a new change But this effect, 
though it really takes place, is not appreciable by the eye : 
though the light thus reflected to the eye is composed of a 
variety of colours, the principal of these only are dis- 
tinguishable." 

Leonardo. 

" No colour reflected on the surface of another colour, 
tinges that surface with its own colour (merely), but will be 

* Page 121, 306, 326, 387. f P««e 3C6. 



Digitized by 



Google 



NOTES. 385 

mixed with various other reflections impinging on the sftme 
surface :" but such effects, he observes elsewhere, " are 
scarcely, if at all, distinguishable in a very difiiised light/'* 

Aristotle. 
'' Thus, all combinations of colours are owing to three 
causes; the light, the medium through which the light 
appears, such as water or air, and lastly the local colour 
from which the light happens to be reflected." 

Leonardo. 

" All illumined objects partake of the colour of the light 
they receive. 

" Every opaque surface partakes of the colour of the 
intervening transparent medium, according to the density of 
such medium and the distance between the eye and the 
object. 

'* The medium is of two kinds ; either it has a surface, 
like water, &c., or it is without a common surface, like the 
air.'t 

In the observations on trees and plants more points of 
resemblance might be quoted ; the passages corresponding 
with Goethe*s views are much more numerous. 

It is remarkable that Leonardo, in opposition, it seems to 
some authorities,^: agrees with Aristotle in reckoning black 
and white as colours, placing them at the beginning and end 
of the scale. § Like Aristotle, again, he frequently makes 
use of the term black, for obscurity ; he even goes further, 

♦ Page 104, 369. 

t Page 236, 260, 328. 

I " De' semplici coloH il primo d il bianco : bench! i filosoft non accettano 
nd il bianco ni il nero nel numero de' colori.'^ — ^p. 125, 141. Elsewhere, 
however, he sometimes adopts the received opinion. 

§ Leon Battista Alberti, in like manner observes : — " Affermano (i filosofi) 
che le specie de* colon sono sette, ciod, che il bianco ed il nero sono i duoi 
estremi, infra i quali ve n'd uno nel meno (rosso) e che infra ciascuno di 
questi duoi estremi e quel del mezio, da ogni parte ve ne sono due altri.*' An 
absurd statement of Lomano, p. 190, is copied verbatim from Lodovico Dolce 

2c 



Digitized by 



Google 



386 NOTES. 

(or he seems to consider that blue may be produced bj the 
actual mixture of black and white^ provided they are pure.* 
The ancient author> however^ explains himself on this point 
as follows — " We must not attempt to make our observa- 
tions on these effects by mixing colours as painters mix them^ 
but by remarking the appearances as produced by the rays 
of light mingling with each other/'f 

When we consider that Leonardo's Treatise professes to 
embrace the subject of imitation in painting, and that Aris- 
totle's briefly examines the physical nature and appearance 
of colours, it must be admitted that the latter sustains the 
above comparison with advantage ; and it is somewhat ex- 
traordinary that observations indicating so refined a know- 
ledge of nature, as regards the picturesque, should not have 
been taken into the account, for such appears to be the 
fact, in the various opinions and conjectures that have been 
expressed from time to time on the painting of the Greeks. 
The treatise in question must have been written when 
Apelles painted, or immediately before; and as a proof 

(Somma della Filos. d'Arist.) ; but elsewhere, p. 306, Lomano agrees with 
Alberti. Aristotle seems to have misled the two first, for after saying there 
are seven colours, he appears only to mention six : he says — ** There are seven 
colours, if brown is to be considered equivalent to black, which seems reason- 
able. Yellow, again, may be said to be a modification of white. Between 
these we find red, purple, green, and blue." — De Setmt et Sensiti, Perhaps 
it is in accordance with this passage that Leonardo da Vinci reckons eight 
colours. — Trattato, p. 126. 

♦ Page 122, 142, 237. 

f On the authority of this explanation the word /<(x«v has sometimes been 
translated in the ibregoing extracts o6f cvrtVy, darknett. 

Raffi^llo Borghini, in his attempt to describe the doctrine of Aristotle with 
a view to painting, observes — ^* There are two principles which concur in the 
production of colour, namely, light and transparence." But he soon loses this 
chie to the best part of the ancient theory, and when he has to speak of the 
derivation of colours from white and blade, he evidently understands it in a 
mere atomic sense, and adds — ** I shall not at present pursue the opinion of 
Aristotle, who assumes black and white as principal colours, and considers all 
the rest as intermediate between them." — // RipotOf 1. ii. Accordingly, like 
Lodovico Dolce, he proceeds to a subject where he was more at home, namdy, 
the symbolical meaning of colours. 



Digitized by 



Google 



NOTES. 387 

that Aristotle's remarks on the effect of semi-tranqparent 
mediums were not lost on the artists of his time, the £dllow- 
ing passage from Pliny is sulgoined, for> though it is well 
known, it acquires additional interest from the foregoing 
extracts. 

'' He (Apelles) passed a dark colour over his pictures 
when finished, so thin that it increased the splendour of the 
tints, while it protected the surface from dust and dirt : it 
could only be seen on looking into the picture. The effect 
of this operation, judiciously managed, was to prevent the 
colours from being too glaring, and to give the spectator the 
impression of looking through a transparent crystal. At 
the same time it seemed almost imperceptibly to add a 
certain dignity of tone to colours that were too florid.*' 
'' This,'* says Reynolds, *' is a true and artist-like descrip- 
tion of glazing or scumbling, such as was practised by 
Titian and the rest of the Venetian painters." 

The account of Pliny has, in this instance, internal evi- 
dence of truth, but it is fully confirmed by the following 
passage in Aristotle : — '' Another mode in which the effect 
of colours is exhibited is when they appear through each 
other, as painters employ them when they glaze (l^aXii- 
^vTcr)* a (dark) colour over a lighter one ; just as the sun, 
which is in itself white, assumes a red colour when seen 
through darkness and smoke. This operation also ensures 
a variety of colours, for there will be a certain ratio between 
those which are on the surface and those which are in 
depth." — De Senau et SensUL 

Aristotle's notion respecting the derivation of colours 
from white and black may perhaps be illustrated by the 
following opinion on the very similar theory of Goethe. 

" Goethe and Seebeck regard colour as resulting from 
the mixture of white and black, and ascribe to the different 

* This word is only strictly applied to unctuous substances, and may confirm 
the views of those writers who have conjectured that asphaltum was a chief 
ingredient in the atram$ntum of the ancients. 

2c2 



Digitized by 



Google 



388 NOTES. 

colours a quality of darkness (tnusqav), by the different de 
grees of which they are distinguished, passing from white to 
black through the gradations of yellow, orange, red, violet, 
and blue, while green appears to be intermediate again be- 
tween yellow and blue. This remark, though it has no 
influence in weakening the theory of colours proposed by 
Newton, is certainly correct, having been confirmed experi- 
mentally by the researches of Herschell, who ascertained 
the relative intensity of the different coloured rays by illu- 
minating objects under the microscope by their means^ &c. 

<' Another certain proof of the difference in brightness of 
the different coloured rays is afforded by the phenomena of 
ocular spectra. If, after gazing at the sun, the eyes are 
closed so as to exclude the light, the image of the sun ap- 
pears at first as a luminous or white spectrum upon a dark 
ground, but it gradually passes through the series of colours 
to black, that is to say, until it can no longer be distin- 
guished from the dark field of vision; and the colours 
which it assumes are successively those intermediate be- 
tween white and black in the order of their illumitiating 
power or brightness, namely, yellow, orange, red, violet, 
and blue. If, on the other hand, after looking for some 
time at the sun we turn our eyes towards a white surface^ 
the image of the sun is seen at first as a black spectrum 
upcm the white surface, and gradually passes through the 
different colours from the darkest to the lightest, and at 
last becomes white, so that it can no longer be distinguished 
from the white surface "* — See par. 40, 44. 

It is not impossible that Aristotle's enumeration of the 
colours may have been derived from, or confirmed by, this 
very experiment. Speaking of the after-image of colours 
he says, " The impression not only exists in the sensorium 
in the act of perceiving, but remains when the organ is at 
rest. Thus if we look long and intently on any object, 

« *' Elementi of Physiology," by J. Muller, M.D., translated from the Ger- 
man by WiUiam Baly, M.D. London, 1839. 



Digitized by 



Google 



NOTES. 389 

when we change the direction of the eyes a responding 
colour follows. If we look at the sun, or any other very 
bright object, and afterwards shut our eyes, we shall, as if 
in ordinary vision, first see a colour of the same kind ; this 
will presently be changed to a red colour, then to purple, 
and so on till it ends in black and disappears." — De Insom" 
niis. 

NOTE N.— Par. 246. 
** The appearance of white in the centre, according to 
the Newtonian theory, arises from each line of rays forming 
its own spectrum. These spectra, superposing each other 
on all the middle part, leave uncorrected (unneutralised) 
colours only at the two edges.'' — S. F.* 

NOTE O.— Par. 252. 
These experiments with grey objects, which exhibit dif- 
ferent colours as they are on dark or light grounds, were 
suggested, Goethe tells us, by an observation of Antonius 
Lucas, of Liittich, one of Newton's opponents, and, in the 
opinion of the author, one of the few who made any well- 
founded objections. Lucas remarks, that the sun acts 
merely as a circumscribed image in the prismatic experi- 
ments, and that if the same sun had a lighter background 
than itself, the colours of the prism would be reversed. 
Thus in Goelhe*s experimenls, when the grey disk is on a 
dark ground, it is edged with blue on being magnified; 
when on a light ground it is edged with yellow. Goethe 
acknowledges that Lucas had in some measure anticipated 
his own theory. — Vol. ii. p. 440. 

NOTE P.— Par. 284. 
The earnestness and pertinacity with which Goethe in- 

* This was objected to Goethe when his ** BeytrVge sur Optik" first ap- 
peared ; he answered the objection by a coloured diagram in the plates to the 
" Farbenlehre :*' in this he undertakes to show that the assumed gradual 
" correction" of the colours would produce results different from the actual 
appearance in nature. 



Digitized by 



Google 



390 NOTES. 

sisted that the different colours are not subject to diflerent 
degrees of refrangibiltty are at least calculated to prove that 
he was himself convinced on the subject, and, however ex- 
traordinary it may seem, his cx>nviction appears to have been 
the result of infinite experiments and the fullest ocular evi- 
dence. He returns to the question in the controversial 
division of his work, in the historical part, and again in the 
description of the plates. In the first he endeavours to 
show that Newton's experiment with the blue and red paper 
depends entirely on the colours being so contrived as to 
appear elongated or curtailed by the prismatic borders. 
'' If," he says, " we take a light-blue instead of a dark one, 
the illusion (in the latter case) is at once evident Accord- 
ing to the Newtonian theory the yellow-red (red) is the 
least refrangible colour, the violet the most refrangible. 
Why, then, does Newton place a blue paper instead of a 
violet next the red ? If the fact were as he states it, the 
difierence in the refrangibility of the yellow-red and violet 
would be greater than in the case of the yellow-red and 
blue. But here comes in the circumstance that a violet 
paper conceals the prismatic borders less than a dark- blue 
paper, as every observer may now easily convince himself," 
&c. — Polemischer Theil, par. 45. Desaguliers, in repeat- 
ing the experiment, confessed that if the ground of the 
colours was not black, the effect did not take place so well. 
Goethe adds, *'not only not so well, but not at all." — His- 
torischer Theil, p. 459- Lucas of Liittich, one of Newton's 
first opponents, denied that two differently- coloured silks are 
different in distinctness when seen in the microscope. 
Another experiment proposed by him, to show the un- 
soundness of the doctrine of various refrangibility, was the 
following : — Let a tin plate painted with the prismatic co- 
lours in stripes be placed in an empty cubical vessel, so 
that from the spectator's point of view the colours may be 
just hidden by the rim. On pouring water into this vessel, 
all the colours become visible in the same d^ree ; whereas, 
it was contended, if the Newtonian doctrine were true/some 



Digitized by 



Google 



NOTES. 391 

colours would be apparent before others. — Historischer 
Theil, p. 434. 

Such are the arguments and experiments adduced by 
Goethe on this subject ; they have all probably been an- 
swered. In his analysis of Newton*s celebrated Experi- 
menium Crucis, he shows again that by reversing the pris- 
matic colours (refracting a dark instead of a light object)^ 
the colours that are the most refrangible in Newton s expe- 
riment become the least so^ and vice versa. 

Without reference to this objection^ it is now admitted 
that " the difference of colour is not a test of difference of 
refrangibility, and the conclusion deduced by Newton is no 
longer admissible as a general truths that to the same de- 
gree of refrangibility ever belongs the same colour^ and to 
the same colour ever belongs the same degree of refrangi- 
bility." — ^Brewster's Optics, p. 72. 

NOTE Q.— Par. 387. 

With the exception of two very inconclusive letters to 
Sulpice Boisseree, and some incidental observations in the 
conclusion of the historical portion under the head of en- 
toptic colours, Goethe never returned to the rainbow. 
Among the jplates he gave the diagram of Antonius de Do- 
minis. An interesting chapter on halos, parhelia, and 
paraselenae, will be found in Brewster*s Optics, p. 270. 

NOTE R.— Par. 478. 

The most complete exhibition of the colouring or mant- 
ling of metals was attained by the late Cav. Nobili, pro* 
fessor of physical science in Florence. The general mode 
in which these colours are produced is thus explained by 
him :* — 

'' A point of platinum is placed vertically at the distance 
of about half a line above a lamina of the same metal laid 



* See ** Memorie ed OsMrvazioni, edite et inedite del Cav. Professor No- 
bili," Firenie, 1834. 



Digitized by 



Google 



392 NOTES. 

horizontally at the bottom of a vessel of glass or porcelain. 
Into this vessel a solution of acetate of lead is poured so as 
to cover not only the lamina of platinmn, but two or three 
lines of the point as well. Lastly^ the point is put in com- 
munication with the negative pole of a battery^ and the 
lamina with the positive pole. At the moment in which 
the circuit is completed a series of coloured rings is pro- 
duced on the lamina under the point similar to those ob- 
served by Newton in lenses pressed together/' 

The scale of colours thus produced corresponds very 
nearly with that observed by Newton and others in thin 
plates and films^ but it is fuller^ for it extends to forty-four 
tints. The following list^ as given by Nobili, is divided 
by liim into four series to agree with those of Newton : the 
numbers in brackets are those of Newton's scale. The 
Italian terms are untranslated^ because the colours in some 
cases present very delicate transitions.* 



First Series. 


1 Biondo argentino (4).f 


6. Fulvo acceso. 


2. Biondo. 


7. Rosso di rame (6). 


3. Biondo d'oro. 


8. Ocria. 


4. Biondo acceso (5). 


9. Ocria violacea. 


5. Fulvo. 


10. Rosso violaceo (7). 


Second Series. 


11. Violetto(8). 


20. Giallo acceso. 


12. Indaco ^10). 


21. Giallo-rando. 


13. Blu carico. 


22. Rancio (13). 


14. Blu. 


23. Rancio-rossiccio. 


13. Bluchiaro (11). 


24. Rancio-rosso. 


16. Celeste. 


25. Rosso-rancio. 


17- Celestegiallognolo. 


26. Lacca-rancia (14). 


IH. Giallo chiarissimo (12). 


27. Lacca. 


19. Giallo. 


28. Lacca accesa (15). 



* The colours in some of the compound terms are in a manner mutually 
neutralising ; such terms might, no doubt, be amended, 
t The three first numbers in Newton^s scale are black, blue, and whit«. 



Digitized by 



Google 



NOTES. 393 

TTiird Series. 

29. Lacca-purpurea (I6). 34. Verde-giallo (20). 

30. Lacca-turchiniccia(17). 35. Verde-rancio. 

31. Porpora-verclognola(18). 36. Rancio-verde (21). 

32. Verde (19). 37. Rancio-roseo. 

33. Verde giallognolo. 38. Lacca-rosea (22). 

Fourth Series. 

39' Lacca-violacea (24). 43. Verde-giallo rossiccio 

40. Violaceo-verdognolo (25). (28). 

41. Verde (26). 44. Lacca-rosea (30). 

42. Verde-giallo (27). 

** These tinU," Professor Nobili observes^ " are disposed 
according to the order of the thin mantlings which occasion 
them ; the colour of the thinnest film is numbered 1 ; then 
follow in order those produced by a gradual thickening of 
the medium. I cannot deceive myself in this arrangement, 
for the thin films which produce the colours are all applied 
with the same electro-chemical process. The battery^ the 
solution, the distances, &c., are always the same ; the only 
difierence is the time the e£fect is suffered to last. This 
is a mere instant for the colour of No. I, a little longer for 
No. 2, and so on, increasing for the succeeding numbers. 
Other criterions, however, are not wanting to ascertain the 
place to which each tint belongs." 

The scale differs from that of Newton, inasmuch as there 
is no blue in Nobili's first series and no green in the se- 
cond : green only appears in the third and fourth series. 
" The first series,' says the Professor, " is remarkable for 
the fire and metallic appearance of its tints, the second for 
clearness and brilliancy, the third and fourth for force and 
richness.** The fourth, he observes, has the qualities of 
the third in a somewhat lesser degree, but the two greens 
are very nearly alike. 

It is to be observed, that red and green are the principal 



Digitized by 



Google 



394 NOTES. 

ingredients in the third and fourdi series, blue and yellow 
in the second and first. 

NOTE S.— Par. 485. 

A chapter on entoptic colours, contained in the supple- 
ment to Goethe's works, was translated with the intention 
of inserting it among the notes, but on the whole it was 
thought most advisable to omit it. Like many other parts 
of the '* Doctrine of Colours" it might have served as a 
specimen of what may be achieved by accurate observation 
unassisted by a mathematical foundation. The whole 
theory of the polarization of light has, however, been so 
fully investigated since Goethe's time, that the chapter in 
question would probably have been found to contain very 
little to interest scientific readers, for whom it seems chiefly 
to have been intended. One observation occurs in it which 
indeed has more reference to the arts; in order to make 
this intelligible, the leading experiment must be first de- 
scribed, and for this purpose the following extracts may 
serve. 



'' The experiment, in its simplest form, is to be made as 
follows : — let a tolerably thick piece of plate-glass be cut 
into several squares of an inch and a half ; let these be 
heated to a red heat and then suddenly cooled. The 
squares of glass which do not split in this operation are now 
fit to produce the entoptic colours. 

4. 

" In our mode of exhibiting the phenomenon, the ob- 
server is, above all, to betake himself, with his apparatus 
to the open air. All dark rooms, all small apertures (fora- 



* The numbers, as usual, indicate the corresponding paragraphs iu the 
original. 



Digitized by 



Google 



NOTES. 395 

mina exigua),^ are again to be giren up. A pure> cloud- 
less sky is the source whence we are to derive a satisfactory 
insight into these appearances. 

5. 

'' The atmosphere being clear^ let the observer lay the 
squares above described on a black surface^ so placing them 
that two sides may be parallel with the plane of vision. 
When the sun is low^ let him hold the squares so as to re- 
flect to the eye that portion of the sky opposite to the sun, 
and he will then perceive four dark points in the four cor- 
ners of a light space. l(, after this> he turn towards the 
quarters of the sky at right angles with that where his first 
observation was made, he will see four bright points on a 
dark ground : between the two regions the figures appear 
to fluctuate. 



" From this simple reflection we now proceed to another, 
which, but little more complicated, exhibits the appearance 
much more distinctly. A solid cube of glass, or in its stead 
a cube composed of several plates, is placed on a black 
mirror, or held a little inclined above it, at sun-rise or sun- 
set. The reflection of the sky being now suffered to fall 
through the cube on the mirror, the appearance above de- 
scribed will appear more distinctly. The reflection of the 
sky opposite to the sun presents four dark points on a light 
ground; the two lateral portions of the sky present the 
contrary appearance, namely, four light points on a dark 
ground. The space not occupied by the corner points ap- 
pears in the first case as a white cross, in the other as a 
black cross, expressions hereafter employed in describing 
the phenomena. Before sun-rise or after sun-set, in a very 

* In the historical part, Ooethe has to speak of so many followers of New- 
ton who begin their statements with '* Si per foramen eziguum," that the 
term is a sort of by-word with him. 



Digitized by 



Google 



396 NOTES. 

subdued light, the white cross appears on the side of the 
sun also.^ 

" We thus conclude that the direct reflection of the sun 
produces a light figure, which we call a white cross ; the 
oblique reflection gives a dark figure, which we call a black 
cross. If we make the experiment all round the sky, we 
shall find that a fluctuation takes place in the intermediate 
regions." 

We pass over a variety of observations on the modes of 
exhibiting this phenomenon, the natural transparent sub- 
stances which exhibit it best, and the detail of the colours 
seen withinf them, and proceed to an instance where the 
author was enabled to distinguish the '* direct'* from the 
'' oblique** reflection by means of the entoptic apparatus, 
in a painter's study. 

40. 

'< An excellent artist, unfortunately too soon taken from 
us, Ferdinand Jagemann, who, with other qualifications, had 
a fine eye for light and shade, colour and keeping, had built 
himself a painting-room for large as well as small works. 
The single high window was to the north, facing the most 
open sky, and it was thought that all necessary requisites 
had been sufficiently attended to. 

<^ But after our friend had worked for some time, it ap- 
peared to him, in painting portraits, that the faces he copied 
were not equally well lighted at all hours of the day, and 
yet his sitters always occupied the same place, and the se- 
renity of the atmosphere was unaltered. 

'' The variations of the favourable and unfavourable light 
had their periods during the day. Early in the morning 
the light appeared most unpleasantly grey and unsatisfac- 

• At mid-day on die 24di of June the aadior obserred the white cross re- 
flected from every part of the horiion. At a certain distance from the sun, 
corresponding, he supposes, with the extent of halos, the black cross appeared. 

\ Whence the term entopiic. 



Digitized by 



Google 



NOTES. 397 

tory ; it became better^ till at la^t^ about an hour before 
noon^ the objects had acquired a totally different appear- 
ance. Everything presented itself to the eye of the artist 
in its greatest perfection, as he would most wish to transfer 
it to canvas. In the afternoon this beautiful appearance 
vanished — the light became worse, even in the brightest 
day, without any change having taken place in the atmo- 
sphere. 

'* As soon as I heard of this circumstance, I at once con- 
nected it in my own mind with the phenomena which I had 
been so long observing, and hastened to prove, by a phy- 
sical experiment, what a clear-sighted artist had discovered 
entirely of himself, to his own surprise and astonishment. 

" I had the second* entoptic apparatus brought to the 
spot, and the effect on this was what might be conjectured 
from the above statement. At mid-day, when the artist 
saw his model best lighted, the north, direct reflection gave 
the white cross ; in the morning and evening, on the other 
hand, when the unfavourable oblique light was so implea- 
sant to him, the cube showed the black cross ; in the inter- 
mediate hours the state of transition was apparent.'* 

The author proceeds to recal to his memory instances 
where works of art had struck him by the beauty of their 
appearance owing to the light coming from the quarter op- 
posite the sun, in *' direct reflection," and adds, " Since these 
decided effects are thus traceable to their cause, the friends 
of art, in looking at and exhibiting pictures, may enhance 
the enjoyment to themselves and others by attending to a 
fortunate reflection." 



* Before described : the author describes several others more or less com- 
plicated, and suggests a portable one. ** Such plates, which need only be an 
inch and a quarter square, placed on each other to form a cube, might be set 
in a brass case, open above and below. At one end of this case a black mir- 
ror with a hinge, acting like a cover, might be fastened. We recommend 
this simple apparatus, with which the principal and original experiment may 
be readily made. With this we could, in the longest days, better define the 
circle round the sun where the black cross appears^" &c. 



Digitized by 



Google 



398 NOTES. 

NOTE T.— Par. 496. 

" Since Goethe wrote, all the earths have been decom- 
posed, and have been shown to be metallic bases united 
with oxygen ; but this does not invalidate his statement.'* — 
S.F. 

NOTE U.— Par. 502. 

The cold nature of black and its affinity to blue are 
assumed by the author throughout ; if the quality is opaque, 
and consequently greyish, such an affinity is obvious, but 
in many fine pictures, intense black seems to be considered 
as the last effect of heat, and in accompanying crimson and 
orange may be said rather to present a difference of degree 
than a difference of kind. In looking at the great picture 
of the globe, we find this last result produced in climates 
where the sun has greatest power, as we find it the imme- 
diate effect of fire. The light parts of black animals are 
often of a mellow colour ; the spots and stripes on skins 
and shells are generally surrounded by a warm hue, and 
are brovni before they are absolutely black. In combus- 
tion, the blackness which announces the complete ignition, 
is preceded always by the same mellow, orange colour. 
The representation of this process was probably intended 
by the Greeks in the black and subdued orange of their 
vases : indeed, the very colours may have been first pro- 
duced in the kiln. But without supposing that they were 
ret^ned merely from this accident, the fact that the combi- 
nation itself is extremely harmonious, would be sufficient 
to account for its adoption. Many of the remarks of 
Aristotle* and Theophrastusf on the production of black, 
are derived from the observation of the action of fire, and 
on one occasion, the former distinctly alludes to the terra- 
cotta kiln. That the above opinion as to the nature of 
black was prevalent in the sixteenth century, may be in- 

* «' De Coloribiw." i "De Igne." 



Digitized by 



Google 



NOTES. 399 

ferred fnmi Lomazzo^ who observes, — " Quanto all* origme 
e generazione de' colori, la frigidity e la madre della bian- 
cbezza : il calore e padre del nero."* The positive cold- 
ness of black may be said to b^n when it approaches 
grey. When Leonardo da Vinci says that black is most 
beautiful in shade, he probably means to define its most 
intense and transparent state, when it is furthest removed 
from grey. 

NOTE v.— -Par. 555. 

The nature of vehicles or liquid mediums to combine 
with the substance of colours, has been frequently discussed 
by modem writers on art, and may perhaps be said to have 
received as much attention as it deserves. Reynolds smiles 
at the notion of our not having materials equal to those of 
former times, and indeed, although the methods of indivi- 
duals will always differ, there seems no reason to suppose 
that any great technical secret has been lost. In these in- 
quiries, however, which relate merely to the mechanical 
causes of bright and durable colouring, the skill of the 
painter in the adequate employment of the higher resources 
of his art is, as if by common consent, left out of the account, 
and without departing from this mode of considering the 
question, we would merely repeat a conviction before ex- 
pressed, viz. that the preservation of internal brightness, a 
quality compatible with various methods, has had more to 
do with the splendour and durability of finely coloured pic- 
tures than any vehicle. The observations that follow are 
therefore merely intended to show how far the older written 
authorities on this subject agree with the results of modern 
investigation, without at all assuming that the old methods, 
if known, need be implicitly followed. 

On a careful examination of the earlier pictures, it is said 



* **Trattato,'' &c.p. 191, the rest of the passage, it must be admitted, 
abounds with absurdities. 



Digitized by 



Google 



400 NOTES. 

that a resinous substance appears to have been mingled with 
the colours together with the oil ; that the fracture of the 
indurated pigment is shining, and that the surface resists the 
ordinary solvents.* This admixture of resinous solutions or 
varnishes with the solid colours is not alluded to, as far as 
we have seen, by any of the writers on Italian practice, but 
as the method corresponds with that now prevalent in 
England, the above hypothesis is not likely to be objected to 
for the present. 

Various local circumstances and relations might seem to 
warrant the supposition that the Venetian painters used 
resinous substances. An important branch of commerce 
between the mountains of Friuli and Venice still consists in 
the turpentine or fir-resin. f Similar substances produced 
from various trees, and known under the conunon name of 
balsams,]; were imported from the East through Venice, for 
general use, before the American balsams§ in some degree 
superseded them ; and a Venetian painter, Marco Boschini, 
in his description of the Archipelago, does not omit to speak 
of the abundance of mastic produced in the island of Scio.|| 

The testimonies, direct or indirect, against the employ- 

* See " Marcucci Saggio Analitico-cbimico sopra i colon,'' &c. Rome, 1816, 
and '^ Taylor's Translation of Merim6e on Oil-painting," London, 1839. The 
last-named work contains much useful information. 

t Italian writers of tiie 16th century speak of three kinds. Cardamis says, 
that of the abiet was esteemed most, tiiat of the larix next, and that of the 
picea least. The resin extracted by incision from the last (the pinus abies 
Linnssi) is known by the name of Burgundy pitch ; when extracted by fire it 
is black. The three varieties occur in Italian treatises on art, under Uie 
names of ogUo di abezxo, trenuntina and pece Checa, 

I The concrete balsam benxoe, called by tiie Italians Muzino, and M- 
xoinoj is sometimes spoken of as a varnish. 

$ Marcucci supposes that balsam of copaiba was mixed with the pigments 
by the (later) Venetians. 

II <* L' Archipelago con tutte le Isole," Yen. 1658. The incidental notices 
of the remains of antiquity in this work would be curious and important if 
they could be relied on. In describing the island of Samos, for instance, the 
autiior asserts that the temple of Juno was in tolerable preservation, and that 
the statue was still there. 



Digitized by 



Google 



NOTES, 401 

ment of any such substances by the Venetian painters^ in the 
solid part of their work, seem, notwithstanding, very con- 
clusive ; we begin with the writer just named. In his prin- 
cipal composition, a poem * describing the practice and the 
productions of the Venetian painters, Boschini speaks of 
certain colours which they shunned, and adds : — ■'' In like 
manner (they avoided) shining liquids and varnishes, which 
I should rather call lackers ;f ft)r the surface of flesh, if 
natural and unadorned, assuredly does not shine, nature 
speaks as to this plainly/* After alluding to the possible 
alteration of this natural appearance by means of cosmetics, 
he continues : '* Foreign artists set such great store by these 
varnishes, that a shining surface seems to them the only de- 
sirable quality in art. What trash it is they prize ! fir-resin, 
mastic, and sandarach, and larch-resin (not to say treacle), 
stuff fit to polish boots. ;|; If those great painters of ours 
had to represent armour, a gold vase, a mirror, or anything 
of the kind, they made it shine with (simple) colours.* '§ 

This writer so frequendy alludes to the Flemish painters, 
of whose great reputation he sometimes seems jealous, that 
the above strong expression of opinion may have been 
pointed at them. On the other hand it is to be observed 
that the term farestieri, strangers, does not necessarily mean 
transalpine foreigners, but includes those Italians who were 



* " La Carta del Navegar Pitoresco," Ven. 1660. It is in Ae Venetian 
dialect. 

t Inveriadure (invetriature), literally the glasing applied to earthenware. 
X " O de che strase se fan eavedal ! 
D'ogio d'aveno, mastici e aandraca ; 
E trementina (per no'dir triaca) 
Robe, che ilustrerave pgni stival.'' — ^p. 338. 
The alliteration of the words tntmentina and triaea is of course lost in a 
translation. 

$ " Ili ha fati straluser co' i colori." Boschini was at least constant in his 
opinion. In the second edition of his " Ricche Minere della Pittura Venei- 
iana," which appeared fourteen years after the publication of his poem, he 
repeats that the Venetian painters avoided some colours in flesh ** e similmente 
i lustri e le vemici." 

2 u 



Digitized by 



Google 



402 NOTES. 

not of the Venetian state.* The directions given hj 
Raphael Borghini,'|' and after him by Armenini,^ respect- 
ing the use and preparation of varnishes made from the very 
materials in question, may thus have been comprehended in 
the censure, especially as some of these recipes were copied 
and republished in Venice by Bisagno^§ in 1642 — that is, 
only six years before Boschinrs poem appeared. 

Ridolfi*s Lives of the Venetian Painters|| (1648) may be 
mentioned with the two last His only observation respect- 
ing the vehicle is, that Giovanni Bellini, after introducing 
himself by an artifice into the painting-room of Antonello 
da Messina, saw that painter dip his brush from time to 
time in linseed oil. This story^ related about two hun- 
dred years after the supposed event, is certainly not to be 
adduced as very striking evidence in any way.^ 

Among the next writers, in order of time prior to Bisagno, 
may be mentioned Canepario** (l6l9). His work, " De 
Atramentis" contains a variety of recipes for different pur- 
poses : one chapter, De atramentis diversicdoribus, has a 
more direct reference to painting. His observations under 
this head are by no means confined to the preparation of 
transparent colours, but he says little on the subject of 

* Thus, in the introduction to the <* Ricche Minere," Boechini calls the 
Milanese, Florentine, Lombard, and Bolognese painters, ybre«li#rt. 
t "II Riposo," Firenie, 1584. 

I " De* Veri Precetti della Pittura," Ravenna, 1587. 

{ " Trattato della Pittura fondato nell* autoriti di molti eccellenti in questa 
professione." Venecia, 1642. Bisagno remarks in his preface, that the books 
on art were few, and that painters were in the habit of keeping them secret. 
He acknowledges that he has availed himself of the labours of others, but 
without mentioning his sources : some passages are copied from Lomano. 
He, however, lays claim to some original observations, and sap he had seoi 
much and discoursed with many excellent painters. 

II «* Le Meraviglie dell» Arte," Veneiia, 1648. 

^ It has been conjectured by some that this story proved the immixture of 
varnishes with the colours, and that the oil was only used to dilute them. 
The epitaph on Antonello da Messina which existed in Vasari's time, alludef 
to his having mixed the colours with oil. 

** ** Petri Maria Caneparii De Atramentis ci^juicumque generis," VeneC 
1619. It was republished at Rotterdam in 1718. 



Digitized by 



Google 



NOTES. 403 

varnishes. After describing a mode of preserving white of 
egg, he says^ ''Others are accustomed to mix colours in 
liquid varnish and linseed> or nut-oil ; for a liquid and oily 
varnish binds the (different layers of) colours better toge- 
ther, and thus forms a very fit glazing material.'*'*' On the 
subject of oils he observes, that linseed oil was in great re^ 
quest among painters ; who, however, were of opinion that 
nut-oil^ excelled it " in giving brilliancy to pictures, in pre- 
serving them better, and in rendering the colours more 
vivid."! 

Lomazzo (a Milanese) says nothing on the subject of 
vehicles in his principal work, but in his '' Idea del Tempio 
della Pittura,"J he speaks of grinding the colours " in nut- 
oil, and spike-oil, and other things," the *' and" here evidently 
means or, and by '' other things'* we are perhaps to under- 
stand other oils, poppy oil, drying oils, &c. 

The directions of Raphael Borghini and Vasari § cannot 
^rtainly be considered conclusive as to the practice of the 
Venetians, but they are very clear on the subject of varnish. 
These writers may be considered the earliest Italian autho- 
rities who have entered much into practical methods. In 
the few observations on the subject of vehicles in Leonardo 
da Vinci's treatise, "there is nothing," as M. Merimee ob- 
serves, " to show that he was in the habit of mixing varnish 
with his colours." Cennini says but little on the subject 

* ** Ita quod magb ex biis evadit atramentuin pictura summopere idoneum." 
Thus, itatramenium is to be understood, as usual, to mean a glazing colour, the 
passage can only refer to the unmixture of varnish with the transparent colours 
applied last in order. 

t In a passage that follows respecting the mode of extracting nut-oil, 
Caneparius appears to miittranslate Oalen, c. 7 — ^*' De Simplicium Medica- 
mentorum facultatibus." The obserrations of Oalen on this subject, and on 
the drying property of linseed, may have given the first hint to the inventors of 
oil-painting. The custom of dating die origin of this art from Van Eyck is 
like that of dating the commencement of modem painting from Cimabue. 
The improver is often assumed to be die inventor. 

X Milan, 1590. 

^ The particulars here alluded to are to be found in the first edition of 
Vasari (1550) as wcU as die second. — v. i. c. 21, &c. 

2d2 



Digitized by 



Google 



404 NOTES. 

of oil-painting ; Leon Battista Albert! is theoretical rather 
than practical, and the published extitM^ts of Lorenzo Ghi- 
berti's MS. chiefly relate to sculpture. 

Borghini and Vasari agree in recommending nut-oil in 
preference to linseed-oil ; both recommend adding varnish 
to the colours in painting on walls in oil, *' because the 
work does not then require to be varnished afterwards,** 
but in the ordinary modes of painting on panel or clothe 
the varnish is omitted. Borghini expressly says, that oil 
alone (senza piu) is to be employed ; he also recommends 
a very sparing use of it 

The treatise of Armenini (1587) was published at 
Ravenna, and he himself was of Faenza, so that his autho- 
rity, again, cannot be considered decisive as to the Venetian 
practice. After all, he recommends the addition of '* com- 
mon varnish" only for the ground or preparation, as a con- 
solidating medium, for the glazing colours, and for those 
dark pigments which are slow in drying. Many of his 
directions are copied from the writers last named ; the re- 
cipes for varnishes, in particular, are to be found in Bor- 
ghini. Christoforo Sorte* (1580) briefly alludes to the 
subject in question. After speaking of the methods of dis- 
temper, he observes that the same colours may be used in 
oil, except that instead of mixing them with size, they are 
mixed on the palette with nut-oil, or (if slow in drying) with 
boiled linseed-oil : he does not mention varnish. The 
Italian writers next in order are earlier than Vasari, and 
may therefore be considered original, but they are all very 
concise. 



* <* Oaseiranoni nella Pittura." In Venecia, 1580. Sorte, who, it a];^>ean, 
was a native of Verona, had worked in hb youth widi Oiolio Romano, at 
Mantua, and communicates the methods taught him by that painter, for giving 
the true effects of perspective in compositions of figures. He is, perhaps, th« 
earliest who describes die process of water-colour painting as distinguished 
from distemper and as adapted to landscape, if the art he describes deserve* 
the name. 



Digitized by 



Google 



NOTES. 405 

The treatise of Michael Angelo Biondo* (1549), re- 
markable for its historical mistakes, is not without interest 
in other respects. The list of colours he gives is, in all 
probability, a catalogue of those in general use in Venice at 
the period he wrote. With regard to the vehicle, he merely 
mentions oil and size as the mediums for the two distinct 
methods of oil-painting and distemper, and does not speak 
of varnish. The passages in the Dialc^ue of Donif (1549), 
which relate to the subject in question, are to the same 
effect. "In colouring in oil," he observes, "the most 
brilliant colours (that we see in pictures) are prepared by 
merely mixing them with the end of a knife on the palette.** 
Speaking of the perishable nature of works in oil-painting 
as compared with sculpture, he says, that the plaster of 
Paris (gesso) and mastic, with other ingredients of which 
the ground is prepared, are liable to decay, &c. ; and else- 
where, in comparing painting in general with mosaic, that 
in the former the colours *' must of necessity be mixed with 
various things, such as oils, gums, white or yolk of egg, and 
juice of figs, all which tend to impair the beauty of the tints.** 
This catalogue of vehicles is derived from all kinds of paint- 
ing: to enforce the argument, and is by no means to be 
understood as belong^ing to one and the same method. 

An interesting little work,;]; still in the form of a dialogue 
(Fabio and Lauro), appeared a year earlier; the author, 
Paolo Pino, was a Venetian painter. In speaking of the 
practical methods Fabio obsen^es, as usual, that oil-painting 
is of all modes of imitation the most perfect, but his reasons 
for this opinion seem to have a reference to the Venetian 

* *< Delia nobilissima Pittura e sua Arte," Veneiia, 1549. Biondo U so 
ignorant as to attribute the Last Supper, by Leonardo da Vinci, to Mantegna. 

t " Disegno del Doni," in Veueda, 1549. 

X '^Dialogo di Pittura," Venena, 1548. Pino, in enumerating the cele- 
brated contemporary artists, does not include Paul Veronese, for a very 
obvious reason, that painter being at the time only about 17 years of age. 
Sorte, who wrote thirty years later, mentions ** Teccellente Messer Paulino 
nostro," alone. 



Digitized by 



Google 



406 NOTE*. 

practice of going over tbe work repeatedly. Lauro asks 
whether it is not possible to paint in oil on the dry wall^ as 
Sebastian del Piombo did. Fabio answers, "the work 
cannot last, for the solidity of the plaster is impenetrable^ 
and the colours, whether in oil or distemper, cannot pass 
the surface." This might seem to warrant the inference 
that absorbent grounds were prepared for oil-painting, but 
there are proofs enough that resins as well as oil were used 
with the gesso to make the preparation compact. See Doni, 
Armenini, &c. This writer, again, does not speak of var- 
nish. These appear to be the chief Venetian and Italian 
authorities^ of the sixteenth and part of the following cen- 
tury ; and although Boschini wrote latest, he appears to have 
had his information from good sources, and more than once 
distinctly quotes Palma Giovane. 

In all these instances it will be seen that there is no allu- 
sion to the immixture of varnishes with the solid colours, 
except in painting on walls in oil, and that the processes of 
distemper and oil are always considered as separate arts.^- 

* 

* The Dialogues of Lodovico Dolce, and various other works, are not re- 
ferred to here, as they contain nothing on the subject in question. The Utest 
authority at all connected with the traditions of Venetian practice, is a certain 
Giambatista Volpato, of Bassano : he died in 1706, and had been ultimate 
with Ridolfi* The only circumstance he has transmitted relating to practical 
details is that Giacomo Hassan, in retouching on a dry surface, sometime 
adopted a method commonly practised, he says, by Paul Veronese (and com- 
monly practised still), namely, that of dipping his brush in spirits of turpen- 
tine ; at other times he oiled out the surface in the usual manner. Volpato 
left a MS. which was announced for publication in Vlcenia in 1685, but it 
never appeared ; it, however, afterwards formed the ground-work of Verci's 
** Notisie intorno alia Vita e alle Opere de* Pittori di Bassano." Venezia, 
1775. See also " Lcttcra di Giambatista Roberti sopra GHacomo da Ponte,'' 
Lugano, 1777. Another MS. by Natale Melchiori, of about the same date, it 
preserved at Treviso and Castel Franco : it abounds with historical mistakes ; 
the author says, for instance, that die Pietro Martyre was begun by Gior- 
gione and finished by Titian. The recipes for varnishes and colours are very 
numerous, but they are mostly copied from earlier works. 

t That distemper was not very highly esteemed by the Venetians may be 
inferred from the following observation of Pino : — " H modo di colorir i 
guazio h imperfetto et pid fragile et & me non diletta onde laaciamolo aU' 



Digitized by 



Google 



NOTES. 407 

Od the other hand, the prohibition of Boschini cannot be 
understood to be universal, for it is quite certain that the 
Venetians varnished their pictures when done.* After 
Titian had finished his whole-length portrait of Pope Paul 
III. it was placed in the sun to be varnished. f Again, in 
the archives of the church of S. Niccolo at Treviso a sum 
is noted (Sept. 21, 1521), " per far la vemise da invemisar 
la Pala dell' altar grando/* and the same day a second entry 
appears of a payment to a painter, '' per esser venuto a dar 
la vemise alia Pala," &c.;|; It is to be observed that in 
both these cases the pictures were varnished as soon as 
done;§ the varnish employed was perhaps the thin com- 
pound of naphtha (oglio di sasso) and melted turpentine 
(oglio d'abezzo), described by Borghini, and after him by 
Armenini : the last-named writer remarks that he had seen 

oltremontani i quali sono privi della vera ria." It is, however, certain that 
die Venetians sometimes painted in this style, and Volpato mentions several 
works of &e kind by Bassan, but he never hints that he began his oil pictures 
in distemper. 

* Boschini says, that the Venetians (he especially means Titian) rendered 
their pictures sparkling by finally touching on a dry surface (d tecco). The 
absence of varnish in the solid colours, the retouching with spirit of turpen- 
tine, and even d teccOf all suppose a dull surface, which would require var- 
nish. The latter method, alluded to by Boschini, was an exception to the 
general practice, and not likely to be followed on account of its difficulty. 
Carlo Maratd, on the authority of Palomino, used to say, *' He must be a 
skilful painter who can retouch without oiling out." 

f See a letter by Francesco Bocchi, and another by Vasari, in the " Lettere 
Pittoriche" of Bottari. The circumstance is mentioned incidentally; die 
point chiefly dwelt on is, that some persons who passed were deceived, and 
bowed to the picture, supposing it to be the pope. 

I Federici, " Memorie Trevigiane," Venexia, 1803. The altar-piece of 
S. Niccolo at Treviso is attributed, in the document alluded to, to Fra Marco 
Pensabene, a name unknown ; the painting is so excellent as to have been 
thought worthy of Sebastian del Piombo : for this opinion, however, diere are no 
historical grounds. It was begun in 1520, but before it was quite finished the 
painter, whoever he was, absconded : it was therefore completed by another. 

§ Titian's stay in Rome was short, and with respect to the Treviso altar- 
piece, a week or two only, at most, can have eli^Med between the completbn 
and the varnishing. Cennini, who recommends delaying a year at least be- 
fore varnishing, speaks of pictures in dbtemper. 



Digitized by 



Google 



408 NOTES. 

this varnish used by the best painters in Lombardy, and 
had heard that it was preferred by Corre^o. The conse- 
quence of this immediate varnishing may have been that the 
warm resinous liquid^ whatever it was, became united with 
the colours, and thus at a future time the pigment may have 
acquired a consistency capable of resisting the ordinary sol- 
vents. Not only was the surface of the picture required to 
be warm, but the varnish was applied soon after it was taken 
from the fire.* 

Many of the treatises above quoted contain directions for 
making the colours dry if some of these recipes, and many 
in addition, are to be found in Palomino, who, however de- 
fective as an historian,^; has left very copious practical 
details, evidently of ancient date. His drying recipes are 
numerous, and although sugar of lead does not appear, car- 
denillo (verdigris), which is perhaps as objectionable, is 
admitted to be the best of all dryers. It may excite some 
surprise that the Spanish painters should have bestowed so 
much attention on this subject in a climate like theirs, but 
the rapidity of their execution must have often required 
such an assistance. § 

One circumstance alluded to by Palomino, in his very 
minute practical directions, deserves to be mentioned. After 



* See Borghini, Annenini, their Venetian copjrist Bisagno, and Palomino. 
The last-named writer, though of another school and much more modem, was 
evidently well acquainted with the ancient methods : he says, ** 8e advierte 
que siempre que se huviere de bamizar alguna cosa conviene que la ptntura y 
el bamix estdn calientes." — Ei Mtiseo Pictorico, t. ii. 

t Burnt alum, one of the ingredients recommended, might perhape account 
for a shining fracture in the indurated pigment in some old pictures. 

\ Of the earlier Spanish writers Pacheco may be mentioned next to Palo- 
mino as containing most practical information. Carducho, De Butron, and 
others, seldom descend to such details. Palomino contains all the directions 
of Pacheco, and many in addition. 

$ See Cean Bermudez, ** Sobre U Escuela Sevillana,'' Cadit, 1806. The 
same reasons induced the later Venetian machinists to paint on dark grounds, 
and to make use of (drying) oil in excess. See Zanetti, Delia Pitiura Ftftt^ 
xianoy 1. iv. 



Digitized by 



Google 



NOTES. 409 

saying what colours should be preserved in their saucers 
under water^ and what colours should be merely covered 
with oiled paper because the water injures them> he pro- 
ceeds to communicate *' a curious mode of preserving oil- 
colours/' and of transporting them from place to place. 
The important secret is to tie them in bladders, the mode 
of doing which he enters into with great minuteness, as if 
the invention was recent. It is true, Christoforo Sorte, in 
describing his practice in water-colour drawing, says he was 
in the habit of presenting a certain vegetable green with 
gum-water in a bladder ; but as the method was obviously 
new to Palomino, there seems sufficient reason to believe 
that oil-colours, when once ground, had, up to his time, been 
kept in saucers and preserved under water.* Among the 
items of expense in the Treviso document before alluded 
to, we find " a pan and saucers for the painters.*'! This is 
in accordance with Cennini's directions, and the same sys- 
tem appears to have been followed till after 1 700.;|; 

The Flemish accounts of the early practice of oil-painting 
are all later than Vasari. Van Mander, in correcting the 
Italian historian in his dates, still follows his narrative in 
other respects verbatim. If Vasari 's story is to be accepted 
as true, it might be inferred that the Flemish secret con- 
sisted in an oil varnish like copal. § Vasari says, that Van 

* Borghini, in describing the method of making a gold-iixe (the same as 
Cennini's), speaks of boiling the ** buccie de' colon" in oil ; this only means 
the skin or pellicle of the colour itself — in fact, he proceeds to say that they 
dissolve in boiling. Vasari, in describing the same process, uses the expres- 
sion ** colori seccaticci.** 

f « Maggio 4 (1520) Per un cadin (catino) per depentori. Per scudellini 
per li depentori.'' — Mem, 7V#v., vol. i. p. 131. Pungileoni ('^Memorie Isto- 
riche di Antonio AUegri") quotes a note of expenses relating to two oil-pictures 
by Paolo Oianotti ; among the items we find <' colori, telari, et brocchette." — 
vol. ii. p. 75. 

X Salmon, in his " Polygraphice'* (1701), gives the following direction : — 
<< Oyl colors, if not presently used, wiU have a skin grow over them, to pre- 
vent which put them into a glass, and put the glass three or four inches under 
water," &c. 

$ This varnish appears to have been known some centuries before Van 
Eyck's time, but he may have been die first to mix it with the colours. 



Digitized by 



Google 



410 NOTES. 

Eyck boiled the oils with other ingredients ; that the ooloun> 
when mixed with this kind of oil, had a very firm con- 
sistence ; that the sm-face of the pictures so executed had a 
lustre, so that they needed no varnish when done ; and that 
the colours were in no danger from water.* 

Certain colours, as is well known, if mixed with oil alone, 
may be washed off after a considerable time. Leonardo 
da Vind remarks, that verdigris may be thus removed. 
Carmine, Palomino observes, may be washed off after six 
years. It is on this account the Italian writers reoonmiend 
the use of varnish with certain colours, and it appears ^e 
Venetians, and perhaps the Italians generally, employed it 
solely in such cases. But it is somewhat extraordinary that 
Vasari should teach a mode of painting in oil so different 
in its results (inasmuch as the work thus required varnish 
at last) from the Flemish method which he so much ex- 
tols — a method which he says the Italians long endeavoured 
to find out in vain. If they knew it, it is evident, assuming 
his account to be correct, that they did not practice it. 

NOTE W.— Par. 608. 

In the second volume Goethe gives the nomenclature of 
the Greeks and Romans at some length. The general no- 
tions of the ancients with regard to colours are thus de- 
scribed : — " The ancients derive all colours from white and 
black, from light and darkness. They say, all colours are 
between white and black, and are mixed out of these. We 
must not, however, suppose that they understand by this a 
mere atomic mixture, although they occasionally use the 
word M-i^tf ;f for in the remarkable passages, where they 
wish to express a kind of reciprocal (dynamic) action of the 
two contrasting principles, they employ the words upacis, 
union, cvyKpujii, combination ; thus, again, the mutual in- 
fluence of light and darkness, and of colours among each 



* See Vasari, Life of Antonello da MeMina. 
t See Note on Par. 177. 



Digitized by 



Google 



NOTES. 411 

otlier^ is described by the word xspivvvdai, an expression of 
similar import. 

''The varieties of colours are di£ferentlj enumerated; 
some mention seven, others twelve^ but without giving the 
complete list. From a consideration of the terminology 
both of the Greeks and Romans, it appears that they some- 
times employed general for specific terms, and vice versa. 

'* Their denominations of colours are not permanently and 
precisely defined^ but mutable and fluctuating, for they are 
employed even with regard to similar colours both on the 
plus and minus side. Their yellow^ on the one hand, in- 
clines to red> on the other to blue ; the blue is sometimes 
green, sometimes red ; the red is at one time yellow, at 
another blue. Pure red (purpur) fluctuates between warm 
red and blue, sometimes inclining to scarlet, sometimes to 
violet 

*' Thus the ancients not only seem to have looked upon 
colour as a mutable and fleeting quality, but appear to have 
had a presentiment of the (physical and chemical) effects 
of augmentation and re-action. In speaking of colours 
they make use of expressions which indicate this knowledge; 
they make yellow redden, because its augmentation tends 
to red ; they make red become yellow, for it often returns 
thus to its origin. 

'*The hues thus specified undergo new modifications. 
The colours arrested at a given point are attenuated by a 
stronger light darkened by a shadow, nay, deepened and 
condensed in themselves. For the gradations which thus 
arise the name of the species only is often given, but the 
more generic terms are also employed. Every colour, of 
whatever kind, can, according to the same view, be multi- 
plied into itself, condensed, enriched, and will in conse- 
quence appear more or less dark. The ancients called 
colour in this state,*' &c. Then follow the designations of 
general states of colour and those of specific hues. 

Another essay on the notions of the ancients respecting 



Digitized by 



Google 



412 NOTES. 

the origin and nature of colour generally, shows bow nearly 
Goethe himself has followed in the same track. The 
dilating effect of light objects^ the action and reaction of the 
retina, the coloured after-image, the general law of contrast, 
the effect of semi-transparent mediums in producing warm 
or cold colours as they are interposed before a dark or light 
background — all this is either distinctly expressed or hinted 
at ; ** but," continues Goethe, '^ how a single element 
divides itself into two, remained a secret for them. They 
knew the nature of the magnet, in amber, only as attraction ; 
polarity was not yet distinctly evident to them. And in 
very modern times have we not found that scientific men 
have still given their almost exclusive attention to attraction, 
and considered the immediately excited repulsion only as a 
mere after-action T' 

An essay on the Painting of the Ancients* was contributed 
by Heinrich Meyer. 

NOTE X.— Par. 670. 

This agrees with the general recommendation so often 
given by high authorities in art, to avoid a tinted look in the 
colour of flesh. The great example of Rubens, whose 
practice was sometimes an exception to this, may however 
show that no rule of art is to be blindly or exclusively 
adhered to. Reynolds, nevertheless, in the midst of his 
admiration for this great painter, considered the example 
dangerous, and more than once expresses himself to this 
effect^ observing on one occasion that Rubens, like Barocdo, 
is sometimes open to the criticism made on an ancient 
painter, namely, that his figures looked as if they fed on 
roses. 

Lodovico Dolce, who is supposed to have g^ven the vhoa 
voce precepts of Titian in his Dialogue, f makes Aretino 

* Vol. ii. p. 69, first edition. 

t ** Dialogo della Pittura, intitolato rAretino." It was fint published at 
^'eiiice in 1557 ; about twenty years before Titian's death. In the dedication 



Digitized by 



Google 



NOTES. 4 1 3 

say : " I would generally banish from my pictures those 
vermilion cheeks with coral lips ; for faces thus treated look 
like masks. Propertius, reproving his Cynthia for using 
cosmetics, desires that her complexion might exhibit the 
simplicity and purity of colour which is seen in the works of 
Apelles." 

Those who have written on the practice of painting have 
always recommended the use of few colours for flesh. 
Reynolds and others quote even ancient authorities as re- 
corded by Pliny, and Boschini gives several descriptions of 
the method of the Venetians, and particularly of Titian, to 
the same effect. •' They used," he says, " earths more than 
any other colour, and at the utmost only added a little ver- 
milion, minium, and lake, abhorring as a pestilence biadetti, 
gialli aanti, amaltini, verdi-axzurri, giallolini,^'* Else- 
where he says,f '* Earths should be used rather than other 
colours :** after repeating the above prohibited list he adds, 
'' I speak of the imitation of flesh, for in other things every 
colour is good ;'* again, '* Our great Titian used to say that 
he who wishes^ to be a painter should be acquainted with 
three colours, white, black, and red."]; Assuming this 

to the senator Loredano, Lodovico Dolce eulogises the work, which he would 
hardly have done if it had been entirely his own : again, the supposition that 
it may have been suggested by Aretino, would be equally conclusive, coupled 
with internal evidence, as to the original source. 

* Introduction to the ** Ricche Minere della Pittura Venenana," Venetia, 
1674. The Italian anuotators on older works on painting are sometimes at a 
loss to find modem terms equivalent to the obsolete names of pigments. (See 
«* Antologia dell *Arte Pittorica.") The colours now in use corresponding with 
Boschini*s list, are probably yellow lakes, smalt, verditer, and Naples yellow. 
Boschini often censures the practice of other schools, and in this emphatic 
condemnation he seems to have had an eye to certain precepts in Lomaao, 
and perhaps, even in Leonardo da Vinci, who, on one occasion, recommends 
Naples yellow, lake, and white for flesh. The Venetian writer often speaks, 
too, in no measured terms of certain Flemish pictures, probably because they 
appeared to him too tinted. 

t " La Carta del Navegar Pitoresco," p. 338. 

X lb. p. 341. In describing Titian's actual practice ("Ricche Minere"), 
he, however, adds yellow (ochre). The red is also particularised, vis., the 
common terra rossa. 



Digitized by 



Google 



414 NOTES. 

aooount to be a little exaggerated^ it is still to be observed 
that the monotony to which the use of few colours would 
seem to tend, is prevented by the nature of the Venetian 
process, which was sufficiently conformable to Goethe*s 
doctrine ; the gradations being multiplied, and the effect of 
the colours heightened by using them as semi-opaque me- 
diums. Immediately after the passage last quoted we read, 
•* He also gave this true precept, that to produce a lively 
colouring in flesh it is not possible to finish at once.*'* As 
these particulars may not be known to all, we add some 
further abridged extracts explaining the order and methods 
of these different operations. 

"The Venetian painters,*' says this writer, f "after 
having drawn in their subject, got in the masses with very 
solid colour, without making use of nature or statues. Their 
great object in this stage of their work was to distinguish 
the advancing and retiring portions, that the figures might 
be relieved by means of chiaro-scuro— one of the most im- 
portant departments of colour and form, and indeed of in- 
vention. Having decided on their scheme of effect, when 
this preparation was dry, they consulted nature and the 
antique ; not servilely, but with the aid of a few lines on 
paper (quattro segni in carta) they corrected their figures 
without any other model. Then returning to their brushes, 
they began to paint smartly on this preparation, producing 
the colour of flesh." The passage before quoted follows, 
stating that they used earths chiefly, that they carefully 
avoided certain colours, " and likewise varnishes and what- 
ever produces a shining surface. J When this second painting 
was dry, they proceeded to scumble over this or that figure 
with a low tint to make the one next it come forward, giving 
another, at the same time, an additional light — for example, 

* High examples here again prove that the opposite system may attain 
results quite as successful. 

f lutroduction to the *' Ricche Minere." 

I See Note to Par. 555. Here again, assuming the description to be cor- 
rect, high authorities might be opposed to the Venetians. 



Digitized by 



Google 



NOTES. 415 

on a head^ a hand, or a foot, thus detaching them, so to speaks 
from the canvas.'* (Tintoret's Prigionia di S. Rocco is here 
quoted.) " By thus still multiplying these well-understood 
retouchings where required, on the dry surface, (a secco) 
they reduced the whole to harmony. In this operation they 
took care not to cover entire figures, but rather went on 
gemming them (gioieUmdole) with vigorous touches. In 
the shadows, too, they infused vigour frequently by glazing 
with asphaltum, always leaving great masses in middle-tint, 
with many darks, in addition to the partial glazings, and 
few lights.*' 

The introduction to the subject of Venetian colouring, in 
the poem by the same author, is also worth transcribing, but 
as the style is quaint and very concise, a translation is neces- 
sarily a paraphrase.'^ 

" The art of colouring has the imitation of qualities for 
its object ; not all qualities, but those secondary ones which 
are appreciable by the sense of sight. The eye especially 
sees colours, the imitation of nature in painting is therefore 
justly called colouring ; but the painter arrives at his end 
by indirect means. He gives the varieties of tone in masses ;f 

* The following quatrain may serve as a specimen ; the author is speaking 
of the importance of the colour of flesh as conducive to picturesque effect : — 
** Importa el nudo ; e come ben Pimporta I 
Un quadro soma nudo 6 come aponto 
Un disnar senza pan, se ben ghe smto. 
Per pill delicia, confetura e torta." — p. 346, 
In his preface he anticiptUes, and thus answers the objections to his Venetian 
dialect — " Mi, che son Venetian in Venetia e che parlo de' Pitori Venetian! 
hd da andarme a stravestirf Ouarda el Cielo." 

f The word Macchioy literally a blot, is generally used by Italian writers, 
by Vasari for instance, for the local colour. Boschini understands by it the 
relative depth of tones rather than the mere difference of hue. " By macchia,*' 
he says, *' I understand that treatment by which the figures are distinguished 
from each other by different tones lighter or darker." — La Carta d§l 
Navegaty p. 328. Elsewhere, " Colouring (as {nractised by the Venetians) 
comprehends both the macchia and drawing ;*' (p. 300) that is, comprehends 
the gradations of light and dark in objects, and the parts of objects, and con- 
sequently, their essential form. ** The macchia,'' he adds, ** is the effect of 
practice, and is dictated by the knowledge of what is requisite for effect." 



Digitized by 



Google 



416 NOTES. 

he smartly impinges lights^ be clothes his preparation with 
more delicate local hues^ he miites» he glazes : thus every- 
thing depends on the method^ on the process. For if we 
look at colour abstractedly^ the most positive may be called 
the most beautiful^ but if we keep the end of imitation in 
view^ this shallow conclusion falls to the ground. The 
refined Venetian manner is very dififerent from mere direct, 
sedulous imitation. Every one who has a good eye may 
arrive at such results, but to attain the manner of Paolo, 
of Bassan, of Palma, Tintoret, or Titian, is a very different 
undertaking.'' * 

The effects of semi-transparent mediums in some natural 
productions seem alluded to in the following passage — 
'* Nature sometimes accidentally imitates figures in stones 
and other substances, and although they are necessarily in- 
complete in form, yet the principle of effect (depth) re- 
sembles the Venetian practice," In a passage that follows 
there appears to be an allusion to the production of the 
atmospheric colours by semi-transparent mediums, f 

NOTE Y.— Par. 672. 

The author's conclusion here is unsatisfactory, for the 
colour of the black races may be considered at least quite 
as negative as that of Europeans. It would be safer to say 
that the white skin is more beautiful than the black, because 
it is more capable of indications of life, and indications of 
emotion. A degree of light which would fail to exhibit the 
finer varieties of form on a dark surface, would be sufficient 
to display them on a light one ; and the delicate mantlings 

* <* Ma Parivar a la maoiera, al trato 
(Verbi gratia) de Paulo, del Bassan, 
Del Vechio, Tentoreto, e di Tician, 
Per Dio, 1'6 cosa da deventar mato."-^. 294, 297. 
f The traces of the Aristotelian theory are quite as apparent in Boschini 
as in the other Itolian writers on art; but as he wrote in the seventeenth 
century, his authority in this respect is only important as an indication of the 
earlier prevalence of the doctrine. 



Digitized by 



Google 



NOTES. 417 

of colour, whether the result of action or emotion^ are more 
perceptible for the same reason. 

NOTE Z.— Par. 69O. 

The author appears to mean that a degree of brightness 
which the organ can bear at all, must of necessity be re- 
moved from dazzling, white light. The slightest tinge of 
colour to this brightness^ implies that it is seen through a 
medium^ and thus, in painting, the lightest, whitest surface 
should partake of the quality of depth. Goethe*s view here 
again accords^ it must be admitted^ with the practice of the 
best colourists, and with the precepts of the highest autho- 
rities. — See Note C. 

NOTE A A.— Par. 732. 

Ample details respecting the opinions of Louis Bertrand 
Castel, a Jesuit^ are given in the historical part. The co- 
incidence of some of his views with those of Goethe is often 
apparent : he objects^ for instance, to the arbitrary selection 
of the Newtonian spectrum; observing that the colours 
change with every change of distance between the prism 
and the recipient surface. — FarbenL vol. ii. p. 527. Jeremias 
Friedrich Gulich was a dyer in the neighbourhood of 
Stutgardt : he published an elaborate work on the technical 
details of his own pursuit. — Farbenl, vol. ii. p. 630. 

NOTE B B.— Par. 748. 

Goethe, in his account of Castel, suppresses the learned 
Jesuit*s attempt at colorific music (the claveqin oculaire), 
founded on the Newtonian doctrine. Castel was compli- 
mented, perhaps ironically, on having been the first to re- 
mark that there were but three principal colours. In 
asserting his claim to the discovery, he admits that there is 
nothing new. In fact, the notion of three colours is to be 
found in Aristotle ; for that philosopher enumerates no 

2 E 



Digitized by 



Google 



418 NOTES. 

more in speaking of the rainbow,* and Seneca calls them by 
their right names, f Compare with Dante, Parad. c. 33. 
The relation between colours and sounds is in like manner 
adverted to by Aristotle ; he says — " It is possible that 
colours may stand in relation to each other in the same 
manner as concords in music> for the colours which are (to 
each other) in proportions corresponding with the musical 
concords, are those which appear to be the most agreeable.''^ 
In the latter part of the l6th century, Arcimboldo, a 
Milanese painter, invented a colorific music ; an account of 
his principles and method will be found in a treatise on 
painting which appeared about the same time. *' Am- 
maestrato dal qual ordine Mauro Cremonese dalla viola, 
musico deir Imperadore Ridolfo II. trov6 sul gravicembalo 
tutte quelle cousonanze che dalF Arcimboldo erano segnate 
coi colori sopra una carta. *'§ 

NOTE C C— Par. 758. 

The moral associations of colours have always been a 
more favourite subject with poets than with painters. This 
is to be traced to the materials and means of description as 
distinguished from those of representation. An image is 
more distinct for the mind when it is compared with some- 
thing that resembles it. An object is more distinct for the 
eye when it is compared with something that differs from it. 
Association is the auxiliary in the one case, contrast in the 

* ** De Meteor.," lib. 3, c. ii. and iv. He observes that this is the oolf 
effect of colour which painters cannot imitate. 

t ** De Ignib. coelest." The description of the prism by Seneca is anotlier 
instance of the truth of CastePs admission. The Roman philosopher's words 
are — ** Virgula solet fieri vitrea, stricta vel pluribus angulis in modo cla?« 
tortuosce; hssc si ex transverso solem accipit colorem talem qualis in area 
videri solet, reddit," &c. 

{ « De Sensu et sensili." 

§ «* n Figino, overo del Fine della Pittura," Mantova, 1591, p. 249. An 
account of the absurd invention of the same painter in composing figures of 
flowers and animals, and even painting portraits in this way, to the great 
delight of the emperor, will be found in the same work. 



Digitized by 



Google 



NOTES. 419 

Other. The poet, of necessity, succeeds best in conveying 
the impression of external things by the aid of analogous 
rather than of opposite qualities : so far from losing their 
effect by this means^ the images gain in distinctness. Com- 
parisons that are utterly false and groundless never strike us 
as sudi if the great end is accomplished of placing the 
thing described more vividly before the imagination. In 
the common language of laudatory description the colour of 
flesh is like snow mixed with vermilion : these are the words 
used by Aretino in one of his letters in speaking of a figure 
of St. John, by Titian. Similar instances without end 
might be quoted from poets : even a contrast can only be 
strongly conveyed in description by another contrast that 
resembles it* On the other hand it would be easy to show 
that w;henever poets have attemped the painter*s method of 
direct contrast^ the image has failed to be striking^ for the 
mind's eye cannot see the relation between two colours. 

Under the same category of effect produced by association 
may be classed the moral qualities in which poets have 
judiciously taken refuge when describing visible forms and 
colours, to avoid competition with the painters* elements^ 
or rather to attain their end more completely. But a 
little examination would show that very pleasing moral 
associations may be connected with colours which would 
be far from agreeable to the eye. All light, positive co- 
lours, light-green, light-purple, white, are pleasing to the 
mind's eye, and no degree of dazzling splendour is offensive. 
The moment, however, we have to do with the actual sense 
of vision, the susceptibility of the eye itself is to be consi- 
dered, the law of comparison is reversed, colours become 
striking by being opposed to what they are not, and their 
moral associations are not owing to the colours themselves. 



Such ( 

" Her beauty hangs upon the cheek of night, 
Like a rich jewel in an Ethiop*B ear." 

Homeo and Ju/iet, 

2 E 2 



Digitized by 



Google 



420 NOTES. 

but to the modifications such colours undergo in consequence 
of what surrounds them. This view, so naturally conse- 
quent on the principles the author has himself arrived at, 
appears to be overlooked in the chapter under considera- 
tion, the remarks in which, in other respects, are acute and 
ingenious. 

NOTE D D.— Par. 849. 

According to the usual acceptation of the term chiaro- 
scuro in the artist world, it means not onlj the mutable 
effects produced by light and shade, but also, the permanent 
differences in brightness and darkness which are owing to 
the varieties of local colour. 

NOTE E E.— Par. 855. 

The mannered treatment of light and shade here alluded 
to by the author is very seldom to be met with in the works 
of the colourists ; the taste may have first arisen from the 
use of plaster-casts, and was most prevalent in France and 
Italy in the early part of the last century. Piazzetta repre- 
sented it in Venice, Subleyras in Rome. In France 
" Restout taught his pupils that a globe ought to be repre- 
sented as a polyhedron. Greuze most implicitly adopted 
the doctrine, and in practice showed that he considered the 
round cheeks of a young girl or an infant as bodies cut into 
facettes."* 

NOTE F F.— Par. 859- 

All this was no doubt suggested by Heinrich Meyer, 
whose chief occupation in Rome, at one time, was making 



* See Taylor's translation of Merim(-e on oil-painting, p. 27. Barry, in A 
letter from Paris, speaks of Restout as the only painter who resembled the 
earlier French masters : the manner in question is undoubtedly sometimes 
very observable in Poutwin. The English artist elsewhere speaks of the 
»♦ broad, happy manner of Subleyras,**— Wor>fr#, London, 1809. 



Digitized by 



Google 



NOT£S. 421 

sepia drawings from sculpture (see Goethe's Italianische 
Reise). It is hardly necessary to say that the observation 
respecting the treatment of the surface in the antique sta* 
tues is rery fanciful. 

NOTE G G.— Par. 863. 

This observation might have been suggested by the draw- 
ings of Claude^ which> with the slightest means^ exhibit an 
harmonious balance of warm and cold. 

NOTE H H.— Par. 865. 

The colouring of Paolo Uccello^ according to Vasari*s 
account of him, was occasionally so remarkable that he 
might perhaps have been fairly included among the in- 
stances of defective vision given by the author. His skill in 
perspective, indicating an eye for gradadon, may be also 
reckoned among the points of resemblance (see Par. 105). 

NOTE I I.— Par. 902. 

The quotation before given from Boschini shows that 
the method described by the author, and which is true with 
regard to some of the Florentine painters, was not prac- 
tised by the Venetians, for their first painting was very 
solid. It agrees, however, with the manner of Rubens, 
many of whose works sufficiently corroborate the account 
of his process given by Descamps. " In the early state of 
Rubens*8 pictures," says that writer,* " everything appeared 
like a thin wash ; but although he often made use of the 
ground in producing his tones, the canvas was entirely 
covered more or less with colour." In this system of leaving 
the shadows transparent from the first, with the ground 
shining through them, it would have been obviously destruc- 
tive of richness to use white mixed with the darks, the 
brightness, in fact, already existed underneath. Hence the 

• •* Ia Vie des Peiutret Flaxnauds/' vol. i. 



Digitized by 



Google 



422 NOTES. 

well-known precept of Rabens to avoid white in the sha- 
dows, a precept, like many others, bdonging to a particular 
practice, and involving all the conditions of that practice.* 
Scarmiglione, whose Aristotelian treatise on colour was 
published in Germany when Rubens was three-and-twenty, 
observes, *' Painters, with consummate art, lock up the 
bright colours with dark ones, and, on the other hand, 
employ white, the poison of a picture, very sparingly." 
(Artificiosissime pictores claros obscuns obsepiant et contra 
candido picturarum veneno summe parcentes, &c.) 

NOTE K K.— Par. 903. 

The practice here alluded to is more frequently observ- 
able in slight works by Paul Veronese. His ground was 
often pure white, and in some of his works it is left as such. 
Titian's white ground was covered with a light warm colour, 
probably at first, auid appears to have been similar to that 
to which Armenini gives the preference, namely, " quella 
che tira al color di came chiarisshna con un non so che di 
fiammeggiante.^f 



* The method he recommended for keeping the colours pure in the light*, 
vix. to place the tints next each other unmixed, and then slightly to unite 
them, may have degenerated to a methodical manner in the hands of his fol- 
lowers. Boschini, who speaks of Rubens himself with due reverence, and 
is for f^m confounding him with his imitators, contrasts such a system 
with that of the Venetians, and adds that Titian used to say, " Chi de irobra- 
tar colori teme», imbrata e machia si medemi." — Carta del Navegar^ p. 341. 
The poem of Boschini is in many respects polemical. He wrote at a time 
when the Flemish painters, having adopted and modified the Venetian pnn- 
<aple8, threatened to supersede the Italian masters in the opinion of the 
world. Their excellence, too, had all the charm of novelty, for in the seveu- 
teenth century Venice produced no remarkable talent, and it was precisely 
the age for her to boast of past glories. The contemptuous manner in which 
Boschini speaks of the Flemish varnishes, of the fear of mixing tints, &c., w 
thus always to be considered with reference to the time and circumstancci. 
So also his boasting that the Venetian masters painted without nature, which 
may be an exaggeration, is pointed at the Naturalitti, Caravaggio and hw 
followers, who copied nature literally. 

t " Veri Precetti della Pitfura," p. 125. 



Digitized by 



Google 



NOTES. 423 

NOTE L L.— Par. 919. 

The notion which the author has here ventured to express 
may have been suggested by the remarkable passage in the 
last canto of Dante's " Paradiso" — 

** Nella profonda e chiara sossutenia, 
Dell' alto lume parremi ire giri 
Di tre colon e dona continenxa," &c. 

After the concluding paragraph the author inserts a letter 
from a landscape-painter, Philipp Otto Runge, which is 
intended to show that those who imitate nature may arrive 
at principles analogous to those of the *' Farbenlehre.** 



THE END. 



London: Printed by W. Clowu and Sovs, Stamford Street. 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 



Digitized by 



Google 




igitized by 



Google 



Digitized by 



Google